- 1 stick (4 oz.) unsalted butter
- 7 bars (3.5 oz. each) semisweet chocolate – 12 oz. chopped, 7.5 oz. cut into 1-inch squares and the rest for garnish
- 1 1/2 cups flour
- 1/4 cup unsweetened cocoa powder
- 1 1/2 teaspoons baking powder
- 1/4 teaspoon salt
- 1 1/4 cups light brown sugar
- 3 eggs, at room temperature
- 1 1/2 teaspoons pure vanilla extract
- 30 marshmallows
- In a medium saucepan, melt the butter and chopped chocolate, stirring frequently, over medium heat. Let cool for 15 minutes.
- In a medium bowl, whisk together the flour, cocoa powder, baking powder and salt.
- Using an electric mixer, beat the sugar, eggs and vanilla at low speed until smooth, 2 minutes. Mix in the cooled chocolate mixture just until blended. Add the flour mixture in 2 batches, mixing on low speed until just combined. Refrigerate the dough for at least 1 hour.
- Preheat oven to 165 degrees C. Line 2 large baking sheets with parchment paper. Using a tablespoon, scoop the dough and roll between your palms to form 1-inch balls. Arrange about 16 balls 2 inches apart on each cookie sheet, flattening slightly. Bake until the tops of the cookies crack, about 12 minutes.
- Meanwhile, snip 8 marshmallows in half crosswise and stick 1 square of chocolate onto each of the cut sides.
- Remove the cookie sheets from the oven; gently press a marshmallow half, chocolate side down, into each cookie. Bake until the marshmallows are just softened, about 4 minutes. Transfer the pans to racks to cool for 5 minutes; grate the remaining chocolate over the hot cookies. Using a spatula, transfer the cookies to the racks; let cool. Repeat the process with the remaining dough, marshmallows and chocolate. Bake each batch on a clean sheet of parchment.