Weigh out ingredients
You'll need all-purpose flour, baking powder, espresso powder, sugar, brown sugar, chocolate, butter, eggs, cocoa powder, and peppermint extract.
Make the dough
Whisk together the dry ingredients. In a separate bowl, melt the chocolate and butter. Bloom the cocoa powder with water. Beat the eggs and sugars together, then fold in the two chocolate mixtures. Finally, fold in the dry ingredients.
Bake the cookies for about 10 minutes at 350 degrees F. Allow them to cool completely on the baking sheet.
Make the ganache
Make the whipped white chocolate ganache by heating the heavy cream and white chocolate. Chill overnight, then whip until thick. Add more heavy cream and whisk until stiff peaks form.
Assemble and enjoy!
Pipe the whipped white chocolate ganache on one cookie, then gently press another on top. Assemble all of the sandwich cookies and enjoy!