Peppermint White Chocolate Ganache
20 (95g) peppermint hard candies, unwrapped
½ cup (115g) heavy cream
6 ounces (170g) finely chopped white chocolate
Pinch of fine sea salt
10 tablespoons (142g) unsalted butter, at room temperature
⅔ cup (132g) granulated sugar
¼ cup (53g) light brown sugar
1 large (56g) egg, at room temperature
1 large (21g) egg yolk, at room temperature
1 teaspoon vanilla extract
¼ teaspoon peppermint extract
2 cups (240g) all-purpose flour
½ cup (43g) cocoa powder (preferably dark or black cocoa)
¼ teaspoon baking powder
½ teaspoon fine sea salt
¾ cup (173g) heavy cream
Reserved crushed peppermints (see step 1)
1. Begin the Filling: Place the peppermints in a large Ziploc bag, and use a rolling pin to crush them into a relatively fine powder. Measure out ⅓ cup of the powder and set aside.
2. Place the remaining peppermint powder and the heavy cream in a small pot. Heat the mixture over low heat until the powder melts and the cream is very hot.
3. Place the white chocolate in a medium heat-safe bowl, then pour the hot cream mixture over the chocolate. Let sit for 30 seconds, then stir until well combined. (The mixture should be completely smooth—if it isn’t, heat it gently over a double boiler.) Stir in the salt. Transfer to a storage container and refrigerate until well chilled.
4. Make the Cookie Dough: Meanwhile, in the bowl of an electric mixer fitted with the paddle attachment, cream the butter, granulated sugar and brown sugar until light and fluffy, about 5 minutes. Add the egg and egg yolk; mix well to combine. Thoroughly scrape down the side of the bowl, then add the vanilla and peppermint extracts and mix to combine.
5. In a small bowl, whisk together the flour, cocoa powder, baking powder and salt; add to the mixer and mix until just incorporated. Scrape down the side of the bowl, then mix again briefly on low speed to make sure everything is combined. Divide the dough in half and form each half into a 1-inch-thick disk. Wrap each disk tightly in plastic wrap and refrigerate for at least 1 hour (and up to overnight).
6. With the oven racks in the upper and lower third of your oven, preheat it to 325°F. Line two baking sheets with parchment paper.
7. On a lightly floured surface, roll out one portion of dough to ⅛ inch thick. Use a 2-inch round cookie cutter to cut the dough and then transfer each round to one of the prepared baking sheets. Repeat with the second disk of dough. Use a mini cookie cutter to cut a shape from the center of each cookie on the second tray; remove the cutouts. Bake until the cookies are set at the edges, 8 to 10 minutes, rotating the trays between racks halfway through baking. Cool completely.
8. Finish the Filling: Transfer the cooled white chocolate mixture to the bowl of an electric mixer fitted with the whisk attachment. Whisk on medium speed until the mixture lightens, about 2 minutes. Add the cream in a slow, steady stream and continue to whisk until the mixture thickens, about 3 minutes. Transfer the mixture to a piping bag fit with a ½-inch-wide pastry tip (or a Ziploc bag with one corner snipped).
9. Flip the cookies without cutouts over, then pipe the filling into the center of each cookie, leaving a ¼-inch border. Sprinkle the reserved peppermint powder on top of the filling, then place one of the cookies with a cutout on top and press down slightly until the filling reaches the edge of the cookies. Let set for 15 minutes before serving. Store in an airtight container at room temperature for up to 5 days.