Step 1

Preheat oven to 375 degrees F. Lightly grease a 9x13'' baking pan and set aside.

Step 2

In a large bowl, cream together the butter and sugar until light and fluffy. 

Step 3

Add the eggs and vanilla and mix well. 

Step 4

Stir in the flour, baking powder and salt. Mix just until combined.

Step 5

Press the sugar cookie mixture gently into an even layer into the bottom of the pan.

Step 6

Bake for 10-13 minutes--DON'T over-bake! You'll be tempted, but the bars should just be barely set in the center and the edges wont be browned at all. 

Step 7

Allow the bars to cool completely before frosting.

Step 8

Add the butter and 2 cups of powdered sugar to a mixing bowl and cream together with an electric mixer until smooth and fluffy, about 3-5 minutes. 

Step 9

Add remaining powdered sugar and vanilla. 

Step 10

Add as much milk as needed to reach a good soft frosting consistency. 

Step 11

Smooth frosting over the bars and sprinkle with toppings.

Step 12

Store bars in an airtight container at room temperature for up to 2 days and in the refrigerator up to 5.