Preheat your oven to 350°F (175°C) and grease a 9-inch cake pan. Set it aside.

In a large mixing bowl, cream together the 10 tablespoons of butter, brown sugar, and white sugar using a stand mixer or hand mixer for about 2 minutes until fluffy.

Add in the egg, egg yolk, and 1 teaspoon of vanilla extract, mixing until fully combined.

Gradually add the flour, baking soda, and salt to the wet mixture. Mix until just incorporated; be careful not to overmix.

Fold in all but 2 tablespoons of the chocolate chips gently.

Press the cookie dough evenly into the prepared cake pan, ensuring it fills the edges. If the dough is sticky, wet your hands lightly to help smooth it out.

Sprinkle the remaining chocolate chips on top and gently press them down into the dough.

Bake in the preheated oven for 22-25 minutes or until golden brown, and a toothpick inserted comes out with a few moist crumbs.

Allow the cake to cool completely on a wire rack, then loosen the edges with a knife and transfer to a platter.

For the frosting, beat the 4 tablespoons of softened butter and 1 1/4 cups of powdered sugar until smooth.

Add 1/2 teaspoon of vanilla and 1-2 tablespoons of milk to reach your desired consistency.

Pipe or spread the frosting around the edges of the cooled cake and add sprinkles for decoration if desired.