Brownie Layer

1. Grease a 13×9-inch baking dish or line with parchment paper.
2. Preheat oven to 325°F.
3. Place butter and chopped white chocolate in a saucepan. Melt over low heat, stirring occasionally.
4. Let cool for 10 minutes.
5. Add in granulated sugar and stir until well-combined.
6. Add in eggs, one at a time, stirring well after each one is added.
7. Stir in all-purpose flour, salt, and vanilla. Mix until well-combined.
8. Stir in the sprinkles.
9. Bake in a 325°F oven for 30 to 35 minutes until a cake tester comes out clean.
10. Cool completely on a wire rack before frosting.

Buttercream Frosting

1. In the bowl of a stand mixer, or a mixing bowl with a hand mixer, beat butter for two minutes.
2. Slowly add in powdered sugar, alternating with cream, adding 1 to 2 tablespoons of cream at a time.
3. Add in vanilla and beat until smooth. (About 2 minutes).
4. Set aside ½ cup of frosting and tint with blue food coloring.
5. Take half of the blue icing and place in a separate bowl. Add red food coloring to make purple icing.
6. Frost cooled bars completely with remaining white icing.
7. Place blue and purple icing in separate decorator bags.
8. Pipe diagonal blue lines across the blondies.
9. Pipe purple lines diagonally across going the opposite direction to form a diamond pattern.
10. Top with sprinkles and enjoy!