Ingredients
1 cup roasted and peeled whole chestnuts (6 ounces)
1 3/4 cups unbleached all-purpose flour
1/3 cup unsweetened Dutch-process cocoa powder
1/2 teaspoon kosher salt
1 cup (2 sticks) unsalted butter, room temperature
1 cup confectioners' sugar
1/4 cup granulated sugar
2 teaspoons pure vanilla extract
Coarse sanding sugar, for rolling
3/4 cup confectioners' sugar
4 tablespoons (1/2 stick) unsalted butter, room temperature
1/2 teaspoon pure vanilla extract
Pinch of kosher salt
Preparation
Cookies: Preheat oven to 325 degrees, with racks in upper and lower thirds.
In a food processor, pulse chestnuts until finely ground. Measure 1/2 cup tightly packed, then reserve remaining for filling. In a medium bowl, whisk together flour, cocoa, and salt. Whisk in 2 tablespoons water (mixture will be clumpy).
In the bowl of an electric mixer fitted with the paddle attachment, beat together butter, confectioners’ sugar, and granulated sugar on medium-high speed until light and fluffy, about 2 minutes. Beat in 1/2 cup packed ground chestnuts and vanilla. Reduce speed to low and beat in flour mixture until just combined.
Place sanding sugar in a small shallow dish. Using a 1-teaspoon ice cream scoop, drop dough into one hand, then roll into a ball. Roll in sanding sugar to coat. Transfer to a parchment-lined baking sheet. Repeat process with remaining dough, spacing 1 inch apart.
Bake, rotating sheets halfway through, until cookies are puffed with slight cracking on top, 12 to 15 minutes. Transfer sheets to a wire rack and let cool completely.
Filling: Meanwhile, in an electric mixer fitted with the paddle attachment, beat together confectioners’ sugar, reserved 1/2 cup ground chestnuts, butter, vanilla, and salt on medium-high speed until light and fluffy, 3 to 5 minutes.
Spread 1/2 teaspoon filling onto bottoms of half the cookies, then sandwich with remaining cookies, pressing gently to spread filling to edges. Filled cookies are best eaten the day they are made.
