For the Cookies:

1. Preheat the oven to 300°F and line a baking sheet with parchment paper. Set aside.
2. In a small bowl, combine the chocolate and the butter. Microwave on low for 1 minute, stopping and stirring the mixture every 15 seconds. Stir until completely melted and smooth. Set aside.
3. Whisk together the flour, baking powder, salt, and cocoa powder. Set aside.
4. Using a stand or hand-held mixer, beat the eggs, sugar, water, vanilla, and mint extract on high until well combined and frothy.
5. Pour in the melted chocolate mixture and mix to combine. Add the dry ingredients in batches, mixing after each addition.
6. Using a small ice cream or cookie scoop, scoop out the batter and place on the prepared baking sheet. Bake for 18 minutes or until the cookies have puffed slightly and cracked. They will deflate slightly as they cool. Cool completely.

For the Filling:

1. While the cookies are baking, make the filling by beating the butter and cream cheese until light and fluffy.
2. Add the powdered sugar and beat the mixture until incorporated. Add a pinch of salt and beat again. The filling should be light, fluffy, and smooth.
3. Spread about 1 tablespoon of the filling on the flat side of a cookie and then top with another cookie, pushing down slightly so the filling goes to edges of the cookies. You can spoon or pipe the filling – whatever is easiest!
4. If desired, roll the sides of the sandwiched cookies in crushed candy canes so they adhere to the filling.
5. Continue until all cookie sandwiches are made. Store in an airtight container for up to a week.