Preheat your oven to 350°F (175°C).

In a large saucepan, melt the butter over medium heat. Once melted, remove from heat and stir in the sugar, eggs, and vanilla extract until well-combined.

Sift in the flour, cocoa powder, and salt, mixing until fully incorporated. Spread the batter into a greased 9x13-inch baking pan.

Bake the brownies for about 20–25 minutes, or until a toothpick inserted comes out with a few moist crumbs. Allow cooling in the pan for about 15 minutes.

In a mixing bowl, cream together the softened butter, brown sugar, and granulated sugar. Add in the milk and vanilla extract, mixing until combined.

Gradually add the flour followed by the chocolate chips. Gently fold until just mixed.

Once the brownies have cooled, evenly spread the cookie dough layer over the brownie base.

In a small saucepan, heat the heavy cream until it just begins to simmer. Remove from heat and add in the chocolate chips, letting them sit for a minute. Stir until smooth and well combined.

Pour the ganache over the cookie dough layer, spreading it evenly. Chill in the refrigerator for at least 30 minutes before cutting into squares.