Line baking sheets with parchment paper.

In a medium sized, microwave safe bowl, melt 6 oz / 175g of the chopped chocolate and butter in the microwave for about 1 minute. Stir until smooth. Set aside to cool to room temperature.

In a stand mixer fitted with the whisk attachment, beat the eggs, sugar, and vanilla until light and foamy, about 5 minutes. Slowly add the melted, cooled, chocolate, and mix them together on low speed just until combined.

In a small bowl, whisk the flour, baking powder, and salt.

Sift the flour mixture into the egg and chocolate mixture. Fold together until combined and then fold in the remaining 6 oz / 175g chopped chocolate.

Let the mixture sit for about 10 minutes or until the batter is firm enough to scoop. This may take longer if the chocolate was not quite room temperature.

Scoop the cookie dough using a #70 (2 1/2-teaspoon) portion scoop onto the prepared baking sheet. You can make the cookies larger or smaller, but it will affect the baking time. Refrigerate the dough balls for about 30 minutes or until they are no longer sticky.

Roll the dough balls between the palms of your hands to create smooth dough. Return to the refrigerator or freezer until ready to bake. You can make the cookies to this point several days ahead and freeze them in zip lock bags.

Preheat the oven to 350°F / 175°C. Line two baking sheets with parchment paper.

Place the chilled dough balls on the cookie sheets, spacing them about 3-inch apart.

Bake, one sheet at a time, in the middle of the oven for about 8 minutes, until the tops are puffed and just start to crack. Take care to not overbake them or they will lose their fudgy brownie texture. I like to bake them the day they will be served, so only bake as many as you need and leave the rest of the dough balls in the freezer for future bakes.

Allow the cookies to cool completely before peeling them off the parchment paper to fill them.

In a medium bowl, mix the butter and confectioners’ sugar with a wooden spoon or handheld mixer until smooth and fluffy. Add the mint extract to taste.

Using a knife or a pastry bag fitted with a round decorating tip, spread the buttercream onto half of the cookies and then top with the remaining cookies.

Dip the edges in the crushed candy cane. Cover and refrigerate until you are ready to serve. These can also be made a day ahead.