LEMON COOKIE BARS

Preheat oven to 350°F. Lightly spray an 8" x 8" (or 9" x 9" for a thinner cookie bar) pan with non-stick cooking spray and line with parchment paper; lightly spray again. In the bowl of a stand mixer fitted with the flat beater, add the egg and butter. Mix on medium speed until blended. Turn the speed to low and add about 1/3 of the cookie mix. Mix until blended and then slowly add the rest of the cookie mix. Continue mixing on medium speed, scraping down bowl as needed, until the mixture comes together. Remove from bowl and either using your fingers (hint: wet your fingertips before patting into the pan) or the back of a spoon, press the cookie dough down into the prepared pan to evenly distribute it in the pan. Bake for 20 minutes, rotating the pan halfway through the baking time. Remove from oven and allow to cool in pan for 10 minutes before turning out onto a cooling rack to cool completely before frosting. The edges will be slightly brown.

Frosting
With a hand held or stand mixer fitted with a paddle or whisk attachment, beat the butter on medium speed until creamy, about 2 minutes. Add icing sugar, lemon juice, heavy cream and zest with the mixer running on low. Increase to high speed and beat for a full 3 minutes. Taste and add salt as needed. Add up to 1/4 cup more icing sugar if frosting is too thin or another tablespoon of cream if frosting is too thick. Frost cookie bars and add rainbow sprinkles on top, if desired.