Preheat oven to 350 degrees F. Line a 13x9" baking pan with foil, extending the foil over the edges of the pan. Spray the foil liberally with cooking spray; set aside.
In the bowl of a stand mixer, cream together the butter & cream cheese until creamy, about 1 minute. Beat in the sugar, powdered sugar and vanilla, followed by the egg. Lastly, beat in the salt, baking soda, baking powder and flour until combined. Press the dough into the prepared pan in an even layer.
Bake the bars for about 20 minutes or until the top is light golden brown and the center is set. Cool completely.
In the bowl of a stand mixer, beat together the butter, cream and vanilla until combined. Beat in the powdered sugar, about 1 cup at a time, until frosting is light and fluffy. Beat in the food coloring.
Spread the frosting in an even layer over the bars and sprinkle liberally with sprinkles. Let set about 1 hour in the fridge before cutting into bars.