Preheat the oven to 350°F (175°C). Grease and flour a 9x13 inch baking pan.

In a mixing bowl, whisk together flour, baking soda, and salt.

In another bowl, cream together the softened butter, granulated sugar, and brown sugar until light and fluffy.

Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Fold in the chocolate chips.

Spread the cookie dough evenly into the prepared baking pan.

Bake for 25-30 minutes or until the edges are golden brown and a toothpick inserted in the center comes out clean.

Allow the cake to cool completely in the pan on a wire rack.

In a mixing bowl, beat the softened butter until creamy.

Gradually add the powdered sugar, mixing on low speed until combined.

Add the heavy cream and vanilla extract, then beat on high speed until light and fluffy.

Once the cookie cake is completely cool, spread the buttercream frosting evenly over the top.

Cut into squares and serve.