Step 1

Preheat the oven to 350 degrees and grease a 9-inch cake pan. Set aside.

Step 2

Using a stand mixer or hand mixer, cream the butter, brown sugar and white sugar together for 2 minutes and then blend in the egg, egg yolk, and vanilla.

Step 3

Add the flour, baking soda and salt and mix until combined. Use a wooden spoon or spatula to mix in all but 2 tablespoons of chocolate chips.

Step 4

Press the cookie dough into the cake pan until evenly distributed. If using your hands, wet your hands lightly so the batter doesn’t stick. Sprinkle the remaining 2 tablespoons of chocolate chips on top and press them down slightly.

Step 5

Bake for 22-25 minutes until the top is golden brown. Let the cookie cool completely and then run a knife along the edge to loosen. Transfer to a platter. Pipe on frosting along the edges and add the sprinkles. If you don’t want to pipe frosting you can simply spread on top.

Step 6

Beat all the frosting ingredients together until smooth, adding milk as needed. If adding food coloring, add one drop at a time, mixing well until desired color. Place into a piping bag and pipe on frosting if desired. Sprinkle on the sprinkles.