Preheat oven to 350 degrees F. Spray a 9-inch pie dish, tart pan or cake pan with nonstick spray.
In a large bowl, cream the softened butter and sugar on medium speed until fluffy and light in color.
Beat in egg, egg yolk and vanilla, scraping down the sides as needed.
In a medium bowl, whisk together the flour, salt, baking powder, baking soda and cornstarch.
With the mixer running on low speed, slowly add the dry ingredients to the wet ingredients. The dough will be quite thick.
Once combined, gently fold in the white chocolate chips and sprinkles using a rubber spatula.
Press the cookie dough evenly into the prepared pan. Bake for 20-25 minutes or until very lightly browned on top. You want the cookie cake to be extra soft in the center, so careful not to overbake.
Allow the cake to cool completely on a wire rack at room temperature before frosting. The center will slightly sink.
For the frosting, beat the butter on medium speed until creamy, about 2 minutes. Add confectioners' sugar, cream, vanilla and almond extracts with the mixer running on low. Increase to high speed and beat for 3 minutes. Add more powdered sugar if frosting is too thin or more cream if frosting is too thick. Add some food coloring into the frosting, if desired.
Frost the cake as desired, I used a Wilton 1M piping tip to decorate the edges.
Using a very sharp knife, cut into slices and serve.
Store cake in an airtight container at room temperature for up to 2 days and in the refrigerator up to 5 days.
