Sugar, egg yolks and vanilla and mix until completely incorporated
Mix in flour, 1 cup at a time, mixing until all flour is mixed in well
Spread in a lightly greased jelly roll pan (15 ½ x 10 inches)
Bake in a 375* oven for 15-17 or until very lightly brown
Let cool completely
For Frosting
Whisk together melted butter and water in a medium bowl. Add in powered sugar and whisk well. You want the frosting to be not too thin and not to thick. (AKA: it can be poured easily.) You may want to add a little more powdered sugar to reach that consistency
Spread frosting on top of bars. Sprinkle with sprinkles evenly over cookie bars