Chocolate-Filled Hazelnut Cookies

3/4 cup hazelnuts, toasted, skins removed

1 cup confectioners' sugar

1 stick plus 1 tablespoon unsalted butter, softened

1/4 teaspoon finely grated lemon zest

1/8 teaspoon salt

1 cup cake flour

1 level tablespoon cocoa powder

3 ounces bittersweet chocolate, chopped

 

Preheat oven to 350 degrees F. Line 2 baking sheets with parchment paper.

 

Grind the nuts with confectioners’ sugar until powdery (do not make into a paste).

 

Blend together the butter, lemon zest, salt, and nut mixture in a large bowl with a spatula or spoon until creamy. Add the flour and cocoa powder, stirring until incorporated. Do not overwork the dough.

 

Roll level 1/2 teaspoons of dough into tiny balls and arrange 1-inch apart on the prepared baking sheets. Bake 1 sheet at a time until lightly crisped, about 12 minutes. Slide the parchment paper with the baked cookies onto a rack to cool.

 

In a microwave-safe bowl, melt the chocolate in the microwave.

 

Spoon a mound, about 1/8 teaspoon, of melted chocolate onto the flat side of a cookie then top with the flat side of another cookie to make a "sandwich". Repeat.

 

Plain cookies can be baked and cooled 1 week ahead and kept at room temperature in an airtight container. Fill when ready to serve.