Preheat your oven to 350°F (175°C) and line an 8x8 inch baking pan with parchment paper.

In a medium saucepan, melt 1 cup of butter over low heat, then stir in 1 cup of unsweetened cocoa powder until smooth.

Add 2 cups of granulated sugar to the melted chocolate mixture, stirring until fully combined.

Crack in 4 eggs, one at a time, mixing well after each addition.

Mix in 1 teaspoon of vanilla extract, followed by 1 cup of all-purpose flour sifted directly into the batter.

Pour the brownie batter into the prepared pan and spread it evenly.

Bake for 25 minutes, or until a toothpick comes out with moist crumbs.

Allow the brownies to cool completely in the pan on a wire rack for about 30 minutes.

In a bowl, combine 1 cup of marshmallow fluff and 2 tablespoons of softened butter until smooth.

Once the brownies are completely cool, generously spread the marshmallow frosting over the top.

For a special touch, lightly toast the marshmallow frosting using a kitchen torch or under a broiler for about 1-2 minutes.

Once toasted, slice the brownies into squares and serve.