Purple Sweet Potato Mont Blanc
The Japanese autumn version of the French classic. Vermicelli-thin strands of sweetened purple sweet potato piped over a dome of whipped cream on a crisp meringue base.
Servings 4 servings
Ingredients
For the Meringue Bases
- 1 large egg white room temperature
- ¼ cup granulated sugar
- 1 pinch salt
For the Purple Sweet Potato Paste
- 1 lb purple sweet potato beni imo, Okinawan, or Stokes Purple, about 2 medium
- 3 tablespoon unsalted butter softened
- 3 tablespoon sweetened condensed milk
- 2 tablespoon granulated sugar
- 2 to 4 tablespoon heavy cream added a spoonful at a time
- 1 teaspoon dark rum optional
- ⅛ teaspoon salt
For the Cream and Finish
- ¾ cup heavy cream cold
- 1 tablespoon powdered sugar
- ¼ teaspoon vanilla extract
- 2 teaspoon powdered sugar for dusting
Instructions
Bake the Meringue Bases
- Heat the oven to 225°F and line a sheet pan with parchment. Whip the egg white with a pinch of salt to soft peaks, then add the ¼ cup granulated sugar a spoonful at a time and whip until glossy and stiff.
- Pipe or spread four flat discs about 2 ½ inches across. Bake for 75 to 90 minutes, until they lift cleanly from the parchment and sound hollow. Cool completely in the turned-off oven with the door cracked.
Make the Purple Sweet Potato Paste
- Peel the purple sweet potatoes and cut into 1 inch chunks. Steam over simmering water for 18 to 22 minutes, until a knife meets no resistance. Steam rather than roast, as dry oven heat dulls the violet color.
- Press the hot flesh through a fine-mesh sieve, then press it through a second time. This removes the fine fibers that clog a Mont Blanc piping tip and is the single most important step in the recipe.
- Beat the warm sieved sweet potato with the softened butter until smooth, then beat in the condensed milk, granulated sugar, salt and rum. Add heavy cream one tablespoon at a time until the paste holds a ridge but sags slightly at the tip.
- Chill the paste for 30 minutes.
Assemble
- Whip the ¾ cup heavy cream with the powdered sugar and vanilla to firm peaks. Mound a tall rounded dome of cream onto each cooled meringue disc and smooth it into a cone. Chill for 15 minutes.
- Fit a piping bag with a Mont Blanc tip and fill it no more than two-thirds full. Starting at the base of each dome, pipe with steady even pressure while rotating the plate, winding the strands up and over until the cream is completely covered.
- Dust generously with powdered sugar and serve within a couple of hours.
Notes
- Sieve twice: Fine fiber in purple sweet potato clogs the piping tip and breaks the strands. A food processor shortens the fibers, it does not remove them.
- Steam, do not roast: Oven heat caramelizes the sugars and turns the violet flesh brownish.
- Ube is not purple sweet potato: Ube is a yam with a different flavor. Use beni imo, Okinawan, or Stokes Purple sweet potato.
- No Mont Blanc tip? A potato ricer held over the cream dome is the best substitute.
- Storage: Paste keeps 3 days refrigerated, meringues keep 1 week airtight at room temperature, but assembled Mont Blancs soften within a few hours. Assemble to order.