Icing Ingredients (you can half this if you want less icing)
2sticks butterat room temp
4teaspoonsbutter flavoringCan use clear vanilla instead
Melt butter. In large mixing bowl, stir together melted butter, white sugar, and brown sugar by hand until well blended. In separate bowl or measuring cup, beat eggs well.
Make sure mixture isn't too hot. If it is, allow to cool for a few minutes before the next step so you don't cook the eggs.
Add eggs, flour, and flavorings to bowl. Stir well to combine. Stir in rainbow sprinkles, if using.
Grease a 9x13 baking dish and pour batter in. Bake at 350 for 40-45 minutes, or until golden brown and set in the center. Center will still be soft. Allow to cool completely before icing.
To make the icing
In a large bowl, cream the butter and about 1 cup of confectioner's sugar with an electric mixer until light and fluffy. Add the butter flavoring, half of the milk, and remaining sugar and beat again until smooth and creamy, scraping down the sides and adding a little extra milk if needed.
Ice cooled cookie bars while still in the pan. Top with sprinkles, if desired. Allow icing to set by leaving uncovered for about half an hour. Enjoy!