Preheat your oven to 350°F (175°C) and grease two 9-inch round cake pans. Line them with parchment paper for easy cleanup.

In a large bowl, melt the butter and stir in the granulated sugar until well combined.

Add the eggs one at a time, mixing thoroughly after each addition.

Stir in the vanilla extract, then add flour, cocoa powder, and salt, mixing until just combined.

Divide the brownie batter evenly between the prepared pans and bake for 25-30 minutes, or until a toothpick comes out with a few moist crumbs.

Let the brownie layers cool completely in the pans before removing.

Cream together softened butter, brown sugar, and granulated sugar until fluffy.

Add milk and vanilla extract, mixing well.

Blend in flour and salt until just combined, and gently fold in the mini chocolate chips.

Place one brownie layer on a serving plate.

Spread a layer of cookie dough over the brownie, then place the second brownie layer on top, pressing down gently.

Heat heavy cream in a saucepan until simmering, then remove from heat.

Stir in the semi-sweet chocolate chips until smooth.

Pour ganache over the top of the assembled cake.

Let the ganache set for about 10 minutes before slicing and serving.