Preheat your oven to 350°F (175°C). Grease a 9-inch pan or line it with parchment paper. In a medium saucepan, melt the butter and chocolate chips over low heat, stirring until smooth. Remove from heat and stir in the granulated sugar, brown sugar, and cocoa powder.

Add the eggs, one at a time, whisking well after each. Stir in vanilla extract, then gently fold in the flour and salt until combined. Pour the brownie batter evenly into the prepared pan. In a large mixing bowl, cream the softened butter and confectioners’ sugar until smooth and fluffy.

Add in the egg and vanilla extract, beating well. Mix in the cocoa powder, followed by the flour, baking soda, and salt. Fold in the chocolate chips. Drop spoonfuls of cookie dough over the brownie batter, then gently spread it out with a spatula (it doesn’t have to be perfect rustic layers are fine!).

Bake in the preheated oven for 25–30 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs. Allow to cool in the pan for at least 20 minutes before slicing. Serve warm with a scoop of vanilla ice cream or enjoy it as-is.