Preheat your oven to 350°F (175°C).

Lightly grease a 24-cup mini muffin pan with nonstick cooking spray or butter.

Make sure the inside of each cavity is coated so the cookie cups release easily after baking.

Step 2: Cream the Butter and Sugars

In a large mixing bowl, beat the softened butter, granulated sugar, and brown sugar together using an electric mixer.

Continue mixing for approximately 2 minutes, until the mixture looks light and fluffy.

Scrape down the sides of the bowl as needed.

Step 3: Add the Egg and Vanilla

Add the egg and vanilla extract.

Beat until fully combined and smooth. Avoid overmixing once the egg has been incorporated.

Step 4: Mix the Dry Ingredients

In a separate bowl, whisk together the flour, cocoa powder, baking soda, and salt.

Gradually add the dry ingredients to the butter mixture.

Mix on low speed until a soft chocolate dough forms. Stop mixing as soon as no dry flour remains.

Step 5: Fill the Mini Muffin Pan

Divide the dough into 24 equal portions, approximately 1 tablespoon each.

Roll each portion into a small ball and place it inside a greased mini muffin cavity.

Press each dough ball gently into the bottom of the cavity. Avoid pressing it too thin because the dough will spread slightly while baking.

Step 6: Bake the Cookie Cups

Bake for approximately 10 to 12 minutes, or until the edges are set and the centers look slightly soft.

Remove the pan from the oven.

While the cookies are still warm, use the rounded end of a small wooden spoon or a clean measuring spoon to gently press down the center of each cookie.

This creates a little well for the chocolate filling.

If the centers puff up during baking, gently press them again while the cookies are warm.

Step 7: Cool the Cookie Cups

Allow the cookie cups to cool in the muffin pan for approximately 10 minutes.

Carefully loosen the edges with a small silicone spatula or butter knife, then transfer them to a wire rack.

Let them cool completely before adding the chocolate filling.

Step 8: Prepare the Chocolate Ganache

Place the semisweet chocolate chips in a heatproof bowl.

Heat the heavy cream in a small saucepan over medium-low heat until steaming and just beginning to bubble around the edges. Do not let it boil vigorously.

Pour the hot cream over the chocolate chips and let it sit for 2 minutes.

Stir gently from the center outward until the chocolate melts and the mixture becomes smooth and glossy.

Add the vanilla extract and stir again.

Allow the ganache to cool for a few minutes until it thickens slightly but remains easy to spoon.

Step 9: Fill the Cookie Cups

Spoon approximately 1 to 1½ teaspoons of chocolate ganache into the center of each cooled cookie cup.

Fill each well without overflowing the edges.

Allow the chocolate to settle slightly before adding the marshmallows.

Step 10: Add the Marshmallows

Place 3 to 4 mini marshmallows on top of the chocolate filling in each cookie cup.

Gently press them into the ganache so they stay in place.

For an extra festive appearance, add a few mini chocolate chips or a tiny sprinkle of crushed peppermint.

Step 11: Add the Chocolate Drizzle

Melt the remaining chocolate in a microwave-safe bowl using short 15- to 20-second intervals, stirring between each interval.

Drizzle a little melted chocolate over the marshmallows using a spoon or piping bag.

Allow the chocolate to set before serving.

Step 12: Serve and Enjoy

Arrange the finished cookie cups on a festive serving platter.

For a beautiful Christmas presentation, add a little crushed peppermint around the platter and serve alongside mugs of hot cocoa.

Your Hot Cocoa Marshmallow Cookie Cups are ready to enjoy!