Sweet Potato Cake

Preparation

1. For the Cranberry Filling

   Step 1

   Put the simple syrup and water in a saucepan and bring to a boil. Add the cranberries and bring back to a boil. Turn off the heat and leave the cranberries to plump for 30 minutes. Drain well.

2. For the Cake

   Step 2

   Heat the oven to 425°F or 400°F on convection.

   Step 3

   Prick the sweet potatoes in several places with the tip of a paring knife. Place on a piece of heavy-duty aluminum foil and bake until the potatoes are very tender and the juices that have seeped out have caramelized, about 1 hour. When the potatoes are cool enough to handle, peel and put through a food mill to make a puree. Put the puree in a saucepan and cook, stirring often, until the puree is very dry. Measure out 1 1/2 cups.

   Step 4

   Reduce the oven temperature to 375°F (350°F if you’re using convection). Spray fourteen to fifteen 2 x 2-inch ring molds with cooking spray and coat the insides with sugar. Set them on a baking sheet lined with a Silpat or parchment.

   Step 5

   Whisk the flour, baking powder, baking soda, and a pinch of salt together.

   Step 6

   Put the heavy cream, egg yolks, and melted butter in a mixing bowl. Whisk until very smooth but not frothy. Whisk in the warm sweet potato puree. Whisk in the dry ingredients, beating just until smooth.

   Step 7

   Put the egg whites in the bowl of a standing mixer fitted with the whisk. Turn it on to low, and beat the whites gently for 2 minutes, to start establishing a structure. The whites will look frothy but still a bit wet. Turn the speed up to medium and add 3 tablespoons of the granulated sugar. Continue to beat at medium speed until the whites have body and are just shy of having soft peaks. Add 3 more tablespoons of the sugar and continue beating until the whites have formed firm peaks. Add the remaining 2 tablespoons sugar and beat until the whites are glossy and smooth and almost stiff.

   Step 8

   Fold one-quarter of the whites into the batter to lighten it. Fold in the remaining whites, gently but thoroughly.

   Step 9

   Fill a pastry bag with the batter and pipe into the molds, filling them one-quarter of the way up. Make a layer of the cranberry filling, then pipe in more batter to fill the rings two-thirds full. Sprinkle the tops with turbinado sugar. Bake until a knife comes out clean, about 20 minutes, rotating the pan halfway through baking.

   Step 10

   Let cool on a rack for a minute or so, then remove the rings. Let cool completely.

3. For the Cranberry Foam

   Step 11

   Set up an ice bath in a large bowl.

   Step 12

   Put the cranberries and simple syrup in a saucepan. Bring to a boil over medium-high heat, then reduce the heat and simmer until the cranberries pop and have broken down a bit.

   Step 13

   Scrape into a blender and make a smooth puree. Strain through a fine strainer into a medium bowl (discard the solids) and set into the ice bath, stirring often to chill completely.

   Step 14

   Sprinkle the Versa-Whip and xanthan gum over the surface of the cranberry puree and whisk in slowly and thoroughly. Whisk until very light and airy, the consistency of shaving cream. Refrigerate, covered with plastic wrap, until you’re ready to serve or for up to 5 hours.

4. For the Date Puree

   Step 15

   Pit and chop the dates. Put them in a small saucepan with the water and bring to a boil over medium-high heat. Turn off the heat and let the dates sit for 10 minutes.

   Step 16

   Put the dates and liquid in a blender and make a smooth puree. Strain through a fine strainer (discard the solids).

5. To Serve

   Step 17

   Smear a layer of the date puree across half a dessert plate. Set a sweet potato cake on the puree.

   Step 18

   Whip the cranberry foam with a whisk to restore its consistency (it falls sometimes) and put a scoop of it next to the cake. Garnish with a tuile. Repeat for each serving.

6. make it simpler

   Step 19

   Here’s an alternative to the cranberry foam. Make the cranberry puree and mix it with an equal amount of heavy cream. Pour it into a soda siphon and charge it with a cream whipper charger (N2O). Give it a good shake and try a squirt; if it’s not carbonated enough for your liking, use a second charger. Make a variationof the Crispy Almond Phyllo (page 211) to stand in for the tuile; replace the almond flour with whole flax seeds.