This stunning dessert is a simple-to-make icebox cake. Chocolate shavings are easily made with a vegetable peeler.

• Vegetable oil, for pan
• 1 7.4-ounce jar peeled roasted chestnuts
• 1 cup whole milk
• ¼ cup plus 1 tablespoon light-brown sugar
• Pinch of coarse salt
• 3 large egg yolks
• 1 tablespoon cornstarch
• 1 teaspoon pure vanilla extract
• 1 tablespoon unsalted butter, room temperature
• 2 ounces bittersweet chocolate (preferably 61 percent cacao), melted and slightly cooled, plus more for shavings
• 1½ cups cold heavy cream
• 24 chocolate wafer cookies (from 1 package)

1. Lightly coat an 8-inch round cake pan with oil, and line with plastic, leaving a 4-inch overhang.
2. Finely grind chestnuts in a food processor. Heat ground chestnuts, milk, 3 tablespoons sugar, and the salt in a medium saucepan over medium-high heat, stirring occasionally, until bubbles form at edge.
3. Whisk together yolks, cornstarch, and remaining 2 tablespoons sugar in a medium heatproof bowl.
4. Slowly add hot chestnut mixture to yolk mixture, whisking constantly. Return to pan; cook over medium-low heat, whisking constantly, until thick, about 2 minutes. Transfer to the bowl of a mixer. Add vanilla and butter. Beat on medium speed until cool, about 5 minutes. Stir half the chestnut mixture into melted chocolate.
5. Beat 1¼ cups cream until soft peaks form. Using a rubber spatula, gently fold half the whipped cream into plain chestnut mixture and the other half into chocolate-chestnut mixture.
6. Pour chestnut mousse into prepared pan. Cover with 12 chocolate wafers, working in a circular pattern. Top with chocolate-chestnut mousse and remaining 12 chocolate wafers. Fold plastic overhang over top to cover cake. Refrigerate overnight.
7. Uncover cake; place a platter on top, flip, and unmold. Remove plastic. Beat remaining ¼ cup cream until soft peaks form. Spread on top of cake. Garnish with chocolate shavings.

Makes one 8-inch cake; Serves 8.