1 stick (8 tablespoons) unsalted butter
3/4 cup packed dark brown sugar
3/4 cup granulated sugar
2 large eggs
1 teaspoon pure vanilla extract
2 1/4 cups all-purpose flour (see Cook's Note)
3/4 teaspoon baking soda
1 teaspoon fine salt
3 cups semisweet chocolate chips
4 cups mini marshmallows
When measuring flour, we spoon it into a dry measuring cup and level off the excess. (Scooping directly from the bag compacts the flour, resulting in dry baked goods.)