Chocolate-Sweet Potato Parfait

To prepare mousse: Bring 1 inch of water to a boil in a large saucepan fitted with a steamer basket. Add sweet potato, cover and steam until very tender, 15 to 20 minutes. Transfer to a food processor; puree until smooth. You should have 1 1/2 cups.

Combine heavy cream, cocoa, brown sugar, 1 tablespoon vanilla, cinnamon, 1/8 teaspoon salt, allspice and cloves in a small saucepan. Heat over medium heat, whisking, until the mixture looks like a thick, glossy chocolate sauce, 2 to 3 minutes. Add to the food processor and puree until very smooth, scraping down the sides a couple of times. Transfer to a bowl. Press a piece of plastic wrap directly on the surface. Refrigerate for at least 4 hours or up to 5 days.

To prepare meringues: Preheat oven to 300 degrees F. Line a large baking sheet with parchment paper.

Whisk confectioners' sugar and cornstarch in a small bowl. Set aside.

Bring 1 inch of water to a simmer in a medium saucepan over medium heat. Whisk egg whites and granulated sugar in a metal mixing bowl. Place the bowl on top of the saucepan, without touching the water. Continue to whisk the mixture slowly but constantly until just warm to the touch, 1 to 2 minutes.

Remove from heat; add cream of tartar and salt. If using vanilla bean, split the pod in half lengthwise. Use the tip of a paring knife to scrape the seeds into the egg white mixture (or add vanilla extract). Using the whisk attachment, beat with an electric mixer on high speed until the mixture is thick, shiny and holds a stiff peak when the beater is lifted, 3 to 15 minutes, depending on the strength of your mixer. Add vinegar and beat to combine. Gently fold in the reserved sugar mixture.

Dollop 16 tablespoonfuls of the meringue onto the prepared baking sheet to make 2-inch cookies.

Bake the meringues until crispy on the outside and still a little soft in the middle, about 25 minutes. Let cool.

To serve, make 2 alternating layers of mousse and meringues in eight 4-ounce jars or dessert dishes. Dust with cinnamon and serve immediately.