Preheat oven to 350 degrees. Line 9x13 baking dish with parchment paper and lightly spray with nonstick cooking spray. Set aside.
In a large bowl, stir butter and sugar together until light and fluffy. Stir in egg, vanilla and almond extract and whip until fluffy. Scrape the sides and stir again briefly. Stir in remaining dry ingredients and mix until just incorporated. It won't come together as a dough initially, but if you grab a handful, it should hold its shape.
Spread dough into prepared pan and press down evenly. Bake 20-25 minutes or until the edges are golden brown. Remove from oven and cool completely.
Stir all ingredients together until smooth and fluffy. Start by adding 3 tablespoons milk and work up from there until frosting is the desired consistency.
Spread over cooled cookie bars and add sprinkles if desired. Cut into bars and serve.
*Be sure to fluff flour first before spooning into measuring cups and leveling the tops. Not fluffing the flour will mean more flour added to the dough and will make for a stiffer end product.