- 1 cup packed light brown sugar
- 1/2 cup granulated sugar
- 1/2 cup (4 oz.) salted butter, softened
- 1 large egg
- 5 tablespoons whole milk
- 1 1/2 teaspoons vanilla extract
- 2 cups (about 9 oz.) all-purpose flour
- 3 tablespoons unsweetened cocoa
- 1 teaspoon baking soda
- 1/4 teaspoon table salt
- 1 1/2 cups semisweet chocolate chips, divided
- 1/4 cup miniature marshmallows
How to Make It
Preheat oven to 325°F. Lightly coat a 10-inch cast-iron skillet with cooking spray. Beat brown sugar, granulated sugar, and butter with a heavy-duty electric stand mixer at medium speed until light and fluffy. Add egg, milk, and vanilla, beating until blended.
Whisk together flour, cocoa, baking soda, and salt in a bowl. Add to butter mixture gradually, beating at low speed until combined.
Add 1 cup of the chocolate chips; beat until combined.
Spread mixture evenly in prepared skillet. Top with remaining 1/2 cup chocolate chips.
Bake in preheated oven until golden and set, about 50 minutes, topping cookie with miniature marshmallows during the last 30 minutes of baking. Let stand 15 minutes; cut into wedges. Serve with vanilla ice cream.