Preheat your oven to 175°C (350°F) and prepare your cake pans by greasing them and lining the bottoms with parchment paper
Start by heat-treating the flour for the cookie dough by baking it for 5 minutes at 175°C or microwaving it until it reaches a safe temperature, then let it cool completely
In a mixing bowl, cream together butter, granulated sugar, and brown sugar until light and fluffy, about 2 to 3 minutes
Add milk and vanilla extract, mixing until smooth and well combined
Gradually add the heat-treated flour and salt, mixing until a soft dough forms
Fold in mini chocolate chips evenly, then divide the dough into small chunks and refrigerate for at least 30 minutes
In a separate large bowl, beat butter and sugar for the cake layers until pale and fluffy, ensuring proper aeration
Add eggs one at a time, mixing thoroughly after each addition
Mix in vanilla extract for flavor depth
In another bowl, whisk together flour, baking powder, and salt
Add dry ingredients to the wet mixture in batches, alternating with milk, mixing gently each time
Fold in sour cream to enhance moisture and softness
Add mini chocolate chips and mix lightly to distribute evenly
Divide the batter evenly into prepared pans
Press small chilled cookie dough pieces into the batter, ensuring they are slightly covered
Bake for 30 to 35 minutes or until a toothpick inserted in the center comes out clean
Allow cakes to cool in pans for 10 minutes before transferring to a wire rack to cool completely
To prepare buttercream, beat butter until smooth and creamy
Gradually add powdered sugar and beat until fluffy
Mix in brown sugar, flour, milk, vanilla extract, and salt until smooth
Fold in mini chocolate chips for texture
Place one cake layer on a serving plate and spread a thick layer of buttercream evenly
Add a few cookie dough chunks on top for extra richness
Place the next cake layer on top and repeat the process
Apply a thin crumb coat over the entire cake and chill for 20 minutes
Add a final layer of buttercream and smooth it using an offset spatula
Prepare ganache by heating cream and pouring it over chocolate, stirring until smooth
Let ganache cool slightly before pouring it over the cake for a drip effect
Decorate with extra cookie dough pieces and chocolate chips as desired
Chill slightly before slicing for clean layers