Instructions

1. Preheat oven to 350°F and line two baking sheets with parchment paper. Whisk together flour, cocoa, baking powder, and salt in a medium bowl. Place chocolate and butter in a double boiler or in a heat-proof bowl over a saucepan of gently simmering water. Slowly melt the chocolate, stirring occasionally until smooth. Remove from the heat and set aside to cool slightly.
2. Combine eggs, sugars, and vanilla in a large mixer bowl fitted with a whisk attachment and whisk together on medium speed for exactly 5 minutes. Reduce speed to low and beat in melted chocolate for 1 minute. Add flour mixture and mix on low speed for 20 seconds, just until combined. Fold in chocolate chips (dough will resemble a gooey brownie batter).
3. Use a cookie scoop coated lightly with nonstick spray to form the cookies – invert the scoop just above the baking sheets, spacing cookies 3 inches apart. Bake, rotating pans halfway through, for 12 to 14 minutes, until tops are shiny and crackly. Remove from oven and let cookies cool for 10 minutes on baking sheets, then transfer to a wire rack to cool completely.
4. For the filling, combine butter and cream cheese in a mixer bowl and beat until smooth. Mix in salt, vanilla, and peppermint extract until combined. Beat in powdered sugar on low speed until incorporated, then on medium speed until light and airy. Transfer filling to a piping bag.
5. To assemble the cookies, pipe about a tablespoon of filling in the center of half the cookies. Sprinkle with crushed peppermint and top with remaining cookies, pressing gently to adhere. Store cookies in an airtight container in the refrigerator; bring to room temperature before serving.