Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper.

In a large mixing bowl, beat the softened butter, brown sugar, and granulated sugar together until light and fluffy.

Add eggs one at a time, mixing well after each addition, then stir in the vanilla extract.

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

Gradually add the dry mixture to the wet ingredients, mixing until just combined, then fold in chocolate chips and marshmallows.

Scoop tablespoon-sized portions of dough onto the prepared baking sheets, spacing them about 2 inches apart.

Bake for 9-10 minutes, looking for set edges and soft centers.

Cool on baking sheets for 5 minutes before transferring to a wire rack.

In a mixing bowl, beat the softened butter until creamy, then blend in the marshmallow creme.

Gradually add powdered sugar and vanilla, mixing until fluffy.

Frost cooled cookies with the marshmallow frosting using a piping bag or spatula.

Optional: Drizzle melted chocolate or sprinkle crushed candy canes on top for decoration.