Hot Cocoa Cookies Recipe

Preheat the oven to 350ºF (177ºC). Line a large baking sheet with parchment paper or silicone baking mat. Set aside.
In a medium size bowl, combine the Devil's Food Cake mix, egg, and oil. Stir with a large spatula until completely combined.
½ box Devil's Food Cake mix, 1 large egg, 3 Tablespoons (42mL) vegetable oil
Using a mini cookie scoop or a ½ Tablespoon measure, drop mounds of cookie dough onto the prepared baking sheet (you can fit 36 mini cookies on one sheet with 3 rows of 12). Gently roll them into smooth balls with your hands.
Bake the cookies for 4 minutes, remove from the oven, quickly but carefully place 1 cut marshmallow on top of each warm cookie, pressing gently to adhere the marshmallow and also slightly flatten the cookie, then return to the oven for 2 more minutes. The marshmallows will puff up during this time.
16 large marshmallows
Remove the cookies from the oven, allow to cool for 1-2 minutes on the baking sheet (marshmallows will deflate), then transfer cookies to a cooling rack to cool completely before adding chocolate buttercream.

In a small bowl with a handheld mixer or the bowl of a stand mixer fitted with the paddle attachment, cream the butter on medium-high speed until it is light and fluffy, about 1-2 minutes.
¼ cup (57g) unsalted butter
Turn the mixer to low, then add the powdered sugar and cocoa powder and mix until combined. Add the vanilla extract, milk (starting with 1 Tablespoon), and salt, then increase the mixer speed to medium and continue to beat until completely combined. You'll want a consistency you can pipe but don't want it too thin so that it's runny. Add additional milk to thin out but add slowly to achieve the perfect consistency.
1 cup (120g) powdered sugar, 3 Tablespoons (18g) Dutch processed cocoa powder2, ½ teaspoon vanilla extract, 1 to 2 Tablespoons (15-30mL) milk, pinch of salt
Fit a piping bag with a star tip (this is my favorite star tip) or a zip top bag with the corner snipped off. Pipe a swirl of frosting on top of each cooled marshmallow, then garnish with mini chocolate chips, chocolate curls, or chocolate sprinkles. Store leftover cookies in an airtight container at room temperature up to 1 week, but are best enjoyed within 3 days. Do not stack cookies as they will stick together. Cookies freeze well, up to 3 months. Thaw at room temperature, and again, do not stack.