Fudgy Grasshopper Sandwich Cookies

Make the chocolate cookies:

1. Beat butter and 1 cup sugar with a stand mixer fitted with the paddle attachment on medium speed until smooth and fluffy, 2 to 3 minutes, stopping to scrape down sides of bowl as needed. Add egg and vanilla; beat until pale yellow and fully combined, 1 to 2 minutes. Turn mixer off; add flour, cocoa, and salt, and beat on low speed until a soft dough forms, about 2 minutes.

2. Divide dough in half. Press each half into a flat disk, and wrap individually in plastic wrap. Refrigerate until firm, about 1 hour. Meanwhile, line 4 baking sheets with parchment paper.

3. Unwrap 1 chilled dough disk, and transfer to a well-floured work surface. Dust top of dough with flour; roll out to 1/8-inch thickness. Using a 3-inch round cookie cutter, cut out rounds from dough, and arrange at least 1 inch apart on 2 of the prepared baking sheets (12 dough rounds per baking sheet). Set dough scraps aside. Using a 1 3/4-inch round cutter, remove centers from dough rounds on baking sheets. Add removed centers to dough scraps. Repeat rolling and cutting process with reserved dough scraps until you have 24 cut-out dough rounds total between the 2 baking sheets. (These will be the tops of the sandwich cookies.) Transfer both baking sheets to freezer, and chill until firm, at least 15 minutes or up to 6 hours. (If you can’t fit both baking sheets in the freezer at once, consolidate dough rounds onto 1 baking sheet by stacking them, placing a sheet of parchment paper between cookie layers. Before baking, rearrange cookies on the 2 parchment paper–lined baking sheets.)

4. While cookie tops chill, remove remaining dough disk from refrigerator, and unwrap on a floured work surface. Roll out to 1/8-inch thickness. Using a 3-inch round cutter, cut out rounds from dough, and transfer to remaining 2 prepared baking sheets. Repeat rolling and cutting process with reserved dough scraps until you have 24 dough rounds total. (These will be the bottoms of the sandwich cookies.) Discard any remaining dough scraps. Transfer baking sheets to freezer, and chill at least 15 minutes or up to 6 hours.

5. Preheat oven to 350°F with racks in upper third and lower third positions. Generously sprinkle cut-out cookie tops evenly with remaining 1 tablespoon sugar. Bake in preheated oven until cookies are completely matte and fragrant, 10 to 12 minutes, rotating baking sheets between top and bottom racks halfway through bake time. Remove from oven. Let cool completely on baking sheets, about 30 minutes. While cookie tops cool, repeat baking process with cookie bottoms on remaining 2 baking sheets. Remove from oven. Let cool completely on baking sheets, about 30 minutes.

Make the mint ganache:

1. Combine milk, peppermint extract, and desired amount of green gel food coloring in a medium-size microwavable bowl. Stir until evenly tinted green. Stir in white baking chips. Microwave on high until melted and smooth, about 1 minute, stopping to stir every 20 seconds. Set aside.

Make the dark chocolate ganache:

1. Combine chocolate chips and milk in a separate medium-size microwavable bowl. Microwave on high until melted and smooth, about 45 seconds, stopping to stir once after 30 seconds. Transfer mixture to a piping bag or a ziplock plastic bag with a 1/16-inch hole cut in the corner. Set aside.

2. Working with 1 cookie at a time, dollop about 2 teaspoons mint ganache onto center of 1 bottom cookie, and spread evenly, leaving a 1/3-inch border around edge. Drizzle with 4 or 5 parallel lines of dark chocolate ganache. Drag a wooden pick back and forth in an alternating pattern through lines of dark chocolate ganache to create a chevron pattern. Top with a cut-out cookie top, using the excess chocolate around the edge of the bottom cookie as glue. Repeat process with remaining cookies and ganache. Discard any leftover ganache. Let cookies stand at room temperature 2 hours, and serve.