Boniatillo (Cuban Sweet Potato Custard)

If you grew up on sweet potato pie, this one is going to reorganize your head a little.

No crust, no oven, no pumpkin pie spice.

Instead you cook the sweet potato down into a syrup infused with a cinnamon stick and a strip of lime peel, then finish it with egg yolks over low heat until it thickens into something between a custard and a preserve.

It comes out pale gold, not orange, because the traditional version uses boniato.

Boniato, pronounced bow nee AH toe, is the Cuban sweet potato: rough brown skin, white flesh, drier and far less sweet than the orange ones, closer to a chestnut.

I first had this at a Christmas Eve dinner at a friend's house in Tampa, in a tiny cup next to a thimble of coffee, and I ate three of them.

That's when it belongs on the table. Noche Buena, Christmas Eve, the biggest meal of the Cuban year.

The whole thing takes about an hour of stovetop work and then it sits in the fridge and sets on its own.

There's exactly one moment that requires your full attention, which is when the egg yolks go in, and I'll walk you through it.

Get that part right and the rest is just stirring.

Orange sweet potato works too, and I'll tell you honestly what changes.

What Is Boniatillo?

It's a stovetop sweet potato custard from Cuba, served cold in small cups. Not baked, not a pudding thickened with starch.

Boiled boniato gets puréed and cooked into a sugar syrup that's been infused with cinnamon and lime peel.

Then beaten egg yolks are tempered in and the whole thing is stirred over low heat until it thickens and pulls away from the sides of the pan.

The yolks are what make it a custard rather than a sweetened purée, and they're what give it the pale gold color and the richness.

It belongs to a family of Cuban root vegetable desserts that also includes versions made with malanga and yuca.

You'll see it most at Noche Buena and through the holidays, usually alongside turrón and buñuelos.

Cooked a little longer and poured into a shallow pan, it firms up into a sliceable paste, which is why you'll find recipes calling the same dish a paste, a pudding, and a custard.

They're all correct. It's a question of how long you keep the pot on the heat.

Boniato vs Sweet Potato

They're related but they behave differently, and the difference is visible in the finished dessert.

• Boniato. Rough, patchy reddish-brown skin. Flesh is white to pale cream. Drier, starchier, and noticeably less sweet, with a mild chestnut and vanilla note. Fluffy rather than moist when cooked.
• Orange sweet potato. Smooth skin, deep orange flesh, wetter and much sweeter, with that familiar caramelized flavor.

Where to find boniato: Latin and Caribbean markets, most Publix stores in Florida, and many larger H-E-B and Fiesta locations. It's sometimes labeled batata, camote, or Cuban sweet potato. Pick firm ones with no soft spots.

Can you substitute? Yes, and plenty of people do.

Here's exactly what changes: the custard comes out orange instead of pale gold, it's sweeter so you should cut the sugar to 1 ¼ cups, and it holds more water so it'll take a few extra minutes on the heat to thicken.

The flavor is still excellent. It's just no longer the same color as the dessert I was served in Tampa.

Ingredients You'll Need

Eight things, and half of them are aromatics. This is a short list where each item does real work.

• Boniato (1 ½ pounds). Peeled and cut into chunks. Peel it right before cooking, the cut flesh oxidizes fast. Orange sweet potato works, see above.
• Salt (1 teaspoon). For the cooking water. Season the boniato from the inside.
• Granulated sugar (1 ½ cups). Cooked into a light syrup first, not stirred in at the end. That step is what gives the dessert its glossy body.
• Water (1 ½ cups). For the syrup.
• Cinnamon stick (1, about 3 inches). A whole stick, simmered and removed. Ground cinnamon here makes the custard gritty and muddy colored. Save the ground stuff for dusting on top.
• Lime peel (1 wide strip, green part only). Take it off with a vegetable peeler and check the back for white pith, which is bitter. This citrus note is what makes boniatillo taste Cuban rather than generic.
• Egg yolks (3 large, lightly beaten). The whole point. They set the custard and carry the richness.
• Vanilla extract (2 teaspoons) or dry sherry (2 tablespoons). Traditional recipes call for a dry sherry. Vanilla is the common home substitute and it's what I use most of the time.
• Ground cinnamon. For dusting at the end.

How to Make Boniatillo

Everything before the yolks is forgiving. The yolks are the one step that isn't. Read the tempering section before you start.

Cook and Purée the Boniato

Peel the boniato and cut it into 2 inch chunks.

Cover with cold water in a pot, add the salt, and bring to a boil.

Simmer 20 to 25 minutes, until a fork goes through with no resistance at all. Undercooked boniato will not purée smooth, and you can't fix it later.

Drain thoroughly and let it steam dry in the hot pot for a minute.

Mash it, then push it through a fine mesh sieve or work it in a food processor until it's completely smooth. You want zero lumps.

Infuse the Syrup

In a wide heavy saucepan, combine the sugar, water, cinnamon stick, and lime peel.

Bring to a boil, then simmer 10 minutes at a steady bubble until it's a light syrup that coats a spoon thinly.

Fish out the cinnamon stick and the lime peel and discard them.

Add the boniato purée and stir it in until smooth.

Cook over medium-low heat for 15 to 20 minutes, stirring often, until it's thick enough that a spoon dragged across the bottom leaves a track that holds for a second.

Temper the Egg Yolks

This is the part that matters. Take it slowly.

Pull the pan OFF the heat and let it sit for two minutes.

Beat the 3 egg yolks in a small bowl.

Ladle about ½ cup of the hot purée into the yolks in a thin stream while whisking constantly. Then add another half cup the same way.

Now pour that warmed yolk mixture back into the pan, whisking as it goes.

Return the pan to LOW heat and stir constantly with a wooden spoon for 4 to 6 minutes.

It's ready when it visibly thickens and the spoon leaves a clean parted path across the bottom of the pan that fills in slowly.

Do NOT let it boil after the yolks go in. Bubbles mean scrambled eggs.

Stir in the vanilla or sherry off the heat.

Chill and Serve

Divide the warm custard among 8 small cups or ramekins, about ⅓ cup each.

Smooth the tops and press plastic wrap directly onto the surface if you don't want a skin to form.

Refrigerate at least 3 hours, or overnight.

Dust with ground cinnamon right before serving.

Tips for a Smooth Custard

• Sieve the purée. Any lump you leave in the purée is a lump in the finished custard. There's no later stage that smooths it out.
• Off the heat, then temper. Two minutes of resting drops the purée below the temperature that scrambles yolks, and it costs you nothing.
• Thin stream, constant whisk. Dumping hot purée into yolks all at once cooks them instantly. Slow and steady.
• LOW heat afterward, no exceptions. A wide pan helps because it heats evenly and lets you see the bottom.
• The spoon test. Drag a wooden spoon across the pan bottom. When the path stays open for a beat before filling in, it's done.
• Rescue a grainy batch. If you see flecks, pull it off the heat immediately and push the whole thing through a fine mesh sieve while hot. You'll lose a little volume and save the dessert.

Boniatillo con Coco and Other Variations

• Boniatillo con coco. The coconut version, popular enough that it often outranks the classic. Replace the 1 ½ cups water with one 13.5 ounce can of full fat coconut milk, reduce the sugar to 1 cup, and stir in 1 cup of grated coconut in syrup, drained, at the end. Some versions skip the yolks entirely, which makes it a pudding rather than a custard.
• The sliceable paste. Cook it 10 to 15 minutes longer after the yolks, until it pulls cleanly away from the pan sides in a mass. Pour into a loaf pan lined with plastic, chill overnight, and slice. Serve with a slab of white cheese, which is very much how it's done.
• With meringue. Some families top the cups with a soft meringue and brown it lightly. Beat 2 egg whites with ¼ cup sugar to stiff peaks, spoon on, and torch or broil for 60 seconds. It uses up the whites you already have.
• With rum. A tablespoon of aged Cuban style rum in place of half the vanilla.

How to Serve It

Cold, in small cups, with strong coffee. The portion is deliberately small because it's rich.

A third of a cup per person is right. Ramekins, espresso cups, or little glass dessert cups all work.

Dust the ground cinnamon on at the last second so it stays a sharp line of color instead of sinking in.

Serve it with café cubano if you have a moka pot, or any strong dark coffee.

At Noche Buena it goes out alongside turrón, buñuelos, and flan, and people take a little of everything.

Storage

• Refrigerated. Covered, up to 5 days. The flavor is better on day two.
• The skin. A film forms on the surface as it chills, which is harmless. Press plastic wrap onto the surface to prevent it, or just stir it back in.
• Freezing. I don't recommend it. Egg thickened custards separate and go grainy on thawing. The sliceable paste version freezes better if you must, wrapped tightly, up to 1 month.
• Make ahead. This is a genuinely good make ahead dessert. Cook it two days before the meal and dust the cinnamon on at the table.

Frequently Asked Questions

Make this the week before Christmas and keep it in the back of the fridge in little cups.

Pull them out after a long dinner, dust the cinnamon on, and pour something strong to go with it.

It's a small dessert that people remember.

Recipe

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Boniatillo (Cuban Sweet Potato Custard)

Prep Time 15 minutes minutes

Cook Time 45 minutes minutes

Total Time 4 hours hours

Servings 8 small cups

Ingredients

For the Custard

• 1 ½ lb boniato Cuban white sweet potato, peeled and cut into 2 inch chunks
• 1 teaspoon salt for the cooking water
• 1 ½ cups granulated sugar
• 1 ½ cups water
• 1 stick cinnamon about 3 inches, whole
• 1 strip lime peel green part only, no white pith
• 3 large egg yolks lightly beaten
• 2 teaspoon vanilla extract or 2 tablespoon dry sherry

To Finish

• 1 teaspoon ground cinnamon for dusting

Instructions

Cook and Puree the Boniato

• Cover the boniato chunks with cold water in a pot, add the salt, and bring to a boil. Simmer 20 to 25 minutes, until a fork meets no resistance.
• Drain thoroughly and let the chunks steam dry in the hot pot for a minute. Mash, then push through a fine mesh sieve or process until completely smooth with no lumps.

Infuse the Syrup

• In a wide heavy saucepan, combine the sugar, water, cinnamon stick, and lime peel. Bring to a boil, then simmer 10 minutes until it forms a light syrup that thinly coats a spoon. Remove and discard the cinnamon stick and lime peel.
• Stir the boniato puree into the syrup until smooth. Cook over medium-low heat for 15 to 20 minutes, stirring often, until a spoon dragged across the bottom leaves a track that holds for a second.

Temper the Yolks and Chill

• Take the pan off the heat and let it stand 2 minutes. Beat the egg yolks in a small bowl. Ladle ½ cup of the hot puree into the yolks in a thin stream while whisking constantly, then repeat with another ½ cup.
• Pour the warmed yolk mixture back into the pan while whisking. Return to LOW heat and stir constantly with a wooden spoon for 4 to 6 minutes, until it thickens and the spoon leaves a clean parted path across the pan bottom. Do not let it boil.
• Off the heat, stir in the vanilla or sherry. Divide among 8 small cups or ramekins, about ⅓ cup each, and smooth the tops.
• Refrigerate at least 3 hours or overnight. Dust with ground cinnamon just before serving.

Notes

• Sieve the puree: Any lump left in the puree stays in the finished custard.
• Temper off the heat: Rest the pan 2 minutes before adding the yolks, add hot puree to the yolks in a thin stream, and keep the heat LOW afterward. Bubbles mean scrambled eggs.
• Grainy rescue: Push the hot custard through a fine mesh sieve immediately.
• Orange sweet potato swap: Reduce the sugar to 1 ¼ cups and cook a few minutes longer. The custard will be orange rather than pale gold.
• Whole cinnamon stick only: Ground cinnamon in the syrup makes the custard gritty and muddy. Save it for dusting.
• Storage: Refrigerate up to 5 days. Do not freeze the custard version, the yolks separate on thawing.