Preheat oven to 350F degrees. Line an 8-inch or 9-inch square baking pan with aluminum foil, making sure to leave enough overhang on the sides. Set aside.

In a large bowl with a mixer, cream the softened butter for about 1 minute on medium speed. Once light and fluffy, add in white and brown sugar and beat until fluffy and light in color. Beat in egg, egg yolk, almond, and vanilla. Scrape down the sides as needed.

In a medium bowl, whisk together the flour, salt, baking powder, baking soda, and cornstarch. Slowly add the dry ingredients into the wet ingredients. The dough will be thick. Once combined, gently fold in 1/2 cup sprinkles using a rubber spatula.

In the prepared baking pan, press in the cookie dough in an even layer. Because the dough is thick, it takes a little bit of work to press it in evenly.

Bake for 20-23 minutes or until very lightly browned on top. The bars are when extra soft, so be careful not overbake. Allow the bars to cool to room temperature before frosting. The center will slightly sink, which is normal.

Cream the butter until it is light and fluffy, about 2-3 minutes. Next, add in the powdered sugar, beginning with 2 1/4 cups and beat until combined. Add in vanilla and heavy cream and beat until light and fluffy. Salt to taste.

If the frosting is too thin, add in more powdered sugar, 1/4 cup at a time until you reach your desired consistency.

With the aluminum foil overhang, remove cooled bars from the baking pan. Frost the bars with a thick layer of frosting and decorate with extra sprinkles if desired. Cut into bite-sized squares.

Enjoy!