1/3 cup cocoa nibs
1/2 teaspoon kosher salt
3/4 cup (1 1/2 sticks) unsalted butter, softened
1/2 cup unsweetened cocoa powder
2/3 cup dark brown sugar
4 ounces bittersweet chocolate, finely chopped (for filling)
6 ounces bittersweet chocolate, melted in a double boiler
2 tablespoons unsalted butter (for filling)
1 tablespoon vanilla extract
1/4 teaspoon kosher salt (for filling)
1 3/4 cups all-purpose flour
1/4 cup heavy cream (for filling)
1 teaspoon baking soda
Preheat the oven to 350ºF.
To make the cookies, grind the cocoa nibs in a coffee grinder or food processor until a fine powder. In the bowl of a stand mixer with the paddle attachment, combine the butter, ground cocoa nibs, and the sugars on medium speed until well mixed.
Add the melted chocolate and the vanilla. Sift together the dry ingredients and add to the bowl. Mix into a smooth dough and chill in the freezer for 5 minutes.
Transfer the dough to a large surface covered with a layer of parchment paper. Top with another layer of parchment and gently roll the dough into a 1/4-inch-thick sheet.
To prevent the cookies from sticking as you cut them, carefully remove the top layer of parchment and sprinkle some flour over the sheet of dough. Replace the parchment, flip the dough, and release the parchment on the other side.
Cut the dough into 2 1/2-inch round cookies and space 1/2 inch apart on an ungreased cookie sheet. Gather any leftover scraps of dough and roll and cut as described above. Repeat until you have no dough left.
Bake the cookies for about 15 minutes, turning the pan 90 degrees halfway through baking, until you can smell the toasted chocolate. Transfer the cookies to a cooling rack. Cool completely. Once cool, the cookies should be crisp.
To make the filling, place the chocolate, butter, and salt in a medium mixing bowl. In a small saucepan, bring the cream to a boil and pour one-third of the cream over the chopped chocolate to melt the chocolate
Add the rest of the cream and stir until smooth. Let cool to room temperature.
Place half of the cookies with the top side (the most attractive) down. Using a piping bag or a spoon, evenly distribute the filling among those cookies, and close into sandwiches with the remaining cookies
Gently press down. Serve immediately or store the cookies in a cool place.