In a large frying pan over medium heat, melt the butter. Continue stirring the butter using a rubber spatula until the color browns, and the milk deposits on the bottom separate and brown. This takes about 10 minutes. Remove from heat immediately.
1 cup Plus 2 tablespoon Unsalted butter
Pour the butter in a large mixing bowl. Let it sit for 15 minutes.
Preheat oven to 350°F Line two baking sheets with parchment paper. Set aside.
In a large separate bowl, sift the flour. Add in baking powder, baking soda, and salt.
2 ⅓ cups All-purpose flour, ½ teaspoon Baking soda, ½ teaspoon Baking powder, 1 teaspoon Salt
Using the mixing bowl with the browned butter, mix in brown sugar and sugar. Mix in vanilla and eggs. Fold in the dry ingredients.
1 cup Brown sugar, ½ cup White granulated sugar, 1 teaspoon Pure vanilla extract, 2 Large eggs
Fold in the chocolate chips. Use a large cookie scoop (3oz scoop) and scoop 6 cookie dough balls per baking sheet.
1 ½ cups Semi-sweet chocolate chips
Bake for 11 minutes (bake one sheet at a time). Cut the marshmallows in half. Top each warm cookie with 1-2 marshmallow halves. Place back in the oven to bake for 2-3 minutes.
Use your fingers to "smush" the marshmallows down slightly. Top the cookies with extra chocolate chips.
Let the cookies sit on the hot tray for 5 minutes before transferring to a cooling rack. Let it cool for 10 minutes before digging in.