Source: Martha Stewart Cookies
1 3/4 cups all-purpose flour
3/4 cup unsweetened cocoa powder (not dutch process)
1/2 teaspoon baking soda
1/2 teaspoon coarse salt
1/2 cup (1 stick) unsalted butter, room temperature
1 cup granulated sugar
1 large egg
1/2 cup milk
1 teaspoon pure vanilla extract
15 large marshmallows, halved crosswise
3 cups confectioners’ sugar
6 tablespoons unsalted butter, room temperature
1/4 cup plus 1 1/2 tsp. unsweetened cocoa powder (not dutch process)
1/4 cup plus two tablespoons milk
3/4 teaspoon pure vanilla extract
Preheat oven to 375 degrees.
In the bowl of an electric mixer fitted with the paddle attachment, cream together butter and sugar until light and fluffy, about 2 minutes.
Using a tablespoon or 1 3/4-inch ice cream scoop, drop dough onto baking sheets lined with parchment paper, about 2 inches apart. Bake cookies, rotating half way through, until firm 8 to 10 minutes. Remove baking sheets from oven, and immediately place a marshmallow half in the center of each cookie, pressing down slightly. Return to oven, and continue baking until marshmallows begin to melt, 2 to 2 1/2 minutes. Transfer cookies to a wire rack to cool completely before frosting.