Prick the sweet potatoes all over and bake them whole at 425 degrees F for 50 to 60 minutes, until they slump and the skins wrinkle. Baking rather than boiling drives off water and concentrates the sugar.

Cool just enough to handle, scoop out the flesh and discard the skins.

Push the warm flesh through a fine mesh sieve or a potato ricer. Do not use a blender, the blades develop the starch and make the paste gummy. You should have about 2 ½ cups of smooth puree.

In a wide heavy pan over medium heat, stir the sugar, water, canela stick and clove until the sugar dissolves. Add the sieved puree, salt and lime juice.

Cook over medium-low heat, stirring constantly and scraping the whole bottom of the pan, for 25 to 35 minutes. The paste is ready when it goes matte, balls up behind the spatula and pulls cleanly away from the sides in a single mass. Remove the canela stick and clove.

Scrape the paste onto a parchment lined sheet, spread it about 1 inch thick and cool 30 to 40 minutes, until warm rather than hot and no longer sticky to a clean finger.

With lightly wet hands, pinch off about 2 tablespoons at a time and roll each into a log about 2 ½ inches long with tapered ends. Set them on parchment with space between them.

Leave uncovered at room temperature for 4 to 6 hours or overnight, until the surface is dry to the touch. Twist each log in a rectangle of wax paper to store.