Preheat oven to 375. Line a 9 x 13 pan with foil or parchment, and set aside.
In a large bowl or the bowl of a stand mixer, cream together the butter and sugar until light and fluffy. Add the eggs, sour cream, and vanilla, and mix until well combined.
Stir in the flour, baking powder, and salt to form a crumbly dough.
Press the dough into the prepared pan to form an even layer, and poke the dough every few inches with a fork so it will bake evenly.
Bake17-20 minutes or until lightly browned around the edges. Cool completely.
To make the frosting, beat together the butter, powdered sugar, and 1 tablespoon half and half. Add additional half and half as needed to make a smooth frosting. Add the vanilla, salt, and food coloring, and beat on high speed until light and fluffy. Spread over the cooled cookies and add sprinkles. Cut into squares and enjoy!