CHESTNUT CHOCOLATE LAYER CAKE

Steps:

• Preheat the oven to 350°F. Butter two 9 × 2-inch round professional baking pans, and line the bottoms with parchment. Butter the parchment, and set aside.
• Using a chestnut knife or a small paring knife, make an incision about 1/8 inch deep through the shell and into the flesh of each chestnut almost all the way around the circumference of the nut. Transfer to a chestnut pan or rimmed baking pan. Roast in the oven until the chestnuts are tender, about 35 minutes. Turn the oven off. Leaving the pan with the chestnuts in the oven, remove several at a time. Working quickly, place 1 chestnut in a towel, and, holding both, peel the chestnut while still hot. Remove and discard the shells and inner skin; let cool completely. Transfer the chestnuts to the bowl of a food processor. Add 2 tablespoons sugar, and pulse until very finely ground; set aside. Reduce the oven temperature to 325°F.
• Place the egg whites and cream of tartar in the bowl of an electric mixer fitted with the whisk attachment. Beat until foamy on medium-low speed, 5 to 6 minutes. With the mixer running, slowly add 1/2 cup sugar. Raise speed to medium-high; beat until stiff peaks form, 6 to 7 minutes. Transfer the egg white mixture to a bowl.
• Into the bowl of an electric mixer fitted with the paddle attachment, sift together the cake flour, chestnut flour, baking powder, cinnamon, salt, and remaining 6 tablespoons sugar. Add the egg yolks, water, oil, and vanilla; beat on medium speed until smooth and well combined, about 1 minute.
• Using a rubber spatula, carefully and gently fold the flour mixture in 4 or 5 additions into the egg white mixture until well combined. Gently fold in the reserved chestnuts and chocolate. Evenly divide the batter between the prepared cake pans.
• Bake on the same shelf, rotating the pans halfway through baking, until golden and a cake tester inserted into the centers of the cakes come out clean, about 65 minutes. Transfer to a wire rack until completely cool. Invert the pans to remove the cakes. Remove the parchment paper.
• Place 1 layer on a cake round (or directly onto a cake stand or serving platter). Using an offset spatula, spread the pastry cream on top to within 1/2 inch of the edges. Place the other layer on top.
• Pour the ganache on top; carefully spread to about 1/4 inch from the edges. The ganache will overflow slightly and gently brim the edges. Arrange the marrons glacés on top of the cake, spaced evenly. Set the cake in a cool place to allow the ganache to firm.
• Place the chocolate in a small bowl. Bring the cream to a boil in a small saucepan over medium-high heat. Pour the boiling cream over the chocolate. Cover with plastic wrap for several minutes. Remove the wrap, and stir until the chocolate is completely smooth and melted. Set the ganache in a cool place; let stand until thickened to the consistency of thick cake batter, 10 to 15 minutes. to cool. In a medium bowl, sift together the flour, salt, and baking powder; set aside.