I make these cookies with unsweetened dark cocoa powder. If you can’t find the dark variety, regular unsweetened cocoa will work as well.
1/2 cup hazelnuts, chopped
2 cups all-purpose flour
1/2 cup unsweetened dark cocoa powder
1/2 tsp baking soda
1/2 tsp kosher salt
2 1/4 tsp ground cinnamon, divided
1 1/2 cups granulated sugar, divided
1 1/4 cups butter, room temperature, divided
1 extra large egg
1 Tbsp vanilla extract
4 oz bittersweet chocolate, chopped
2 Tbsp hazelnuts, finely chopped
1. Preheat the oven to 350°.
2. In a mini food processor, blender, or spice mill, finely grind 1/2 cup of the hazelnuts. Transfer to a large bowl and add the flour, cocoa, baking soda, salt, and 1 1/4 tsp cinnamon. Mix well.
3. With an electric mixer, beat 1 cup granulated sugar and 1 cup butter until pale and fluffy. Add the egg and vanilla. Stir in the dry ingredients until just combined.
4. In a small bowl, combine 1/2 cup sugar and 1 tsp. cinnamon.
5. Roll rounded tablespoons of dough into balls, then roll in cinnamon sugar to coat. Arrange on baking sheets 2″ apart.
6. Bake until the cookies are puffed and set but still moist, 10 to 12 minutes.
7. Remove the baking sheet from the oven and, using the small end of a melon baller or a rounded measuring teaspoon, immediately make an indentation in the center of each cookie. Transfer the cookies to wire racks to cool.
8. In a small bowl, combine the remaining 4 Tbsp of butter and chocolate. Microwave in 15 second intervals to melt, stirring each time.
9. With a small spoon, fill each cookie with the melted chocolate. Immediately sprinkle with the remaining 2 Tbsp. of finely chopped nuts.
10. Let the chocolate set before storing in air tight containers.