Preheat oven to 350 degrees F. Line a baking sheet with parchment paper and set aside.

In a medium bowl, whisk together flour, cocoa, espresso powder, baking soda, salt, and baking powder. Set aside.

With a stand mixer fitted with the paddle attachment, cream butter and sugars together until smooth. Add in eggs, vanilla extract, peppermint extract, and mix until combined.

With the mixer off, add the dry ingredients and mix on low until just combined. Don’t over mix.

Stir in the chocolate chips.

Scoop about 2 tablespoons of the cookie dough and gently flatten it in the palm of your hand. Place a marshmallow half into the center of the dough. Use your hands to work the dough around the marshmallow so that the marshmallow is covered around the bottom and sides but there is a little marshmallow peeking out the top. You want some of the marshmallow showing on top so the peppermint candies can stick to the marshmallow, but make sure the bottom is covered so the cookies don't stick to the pan.

Bake cookies for 10 to 12 minutes or until the cookies are set around the edges but still soft in the center. Don’t over bake. The cookies will set up as they cool.

Remove from oven and immediately sprinkle with crushed peppermint candy. You can gently press it into the warm cookies so it will stick. Sprinkle with flaky sea salt.

Let the cookies sit on the baking sheet for about 5 minutes. Move to a cooling rack and cool completely.