Ingredients
1 stick unsalted butter, plus more for greasing
2 packages Birthday Cake Oreos, either chocolate, vanilla, or one of each
2 c. semisweet chocolate chips
3/4 c. granulated sugar
3/4 c. brown sugar
4 large eggs
2 tsp. pure vanilla extract
1 1/2 c. birthday cake mix (such as Funfetti), divided
1 tsp. kosher salt
2 c. rainbow sprinkles, divided
1 container vanilla frosting
Preparation
Step 1Preheat oven to 325°, then grease a 9"-x-13" pan and line with parchment paper. Line bottom of pan with Birthday Cake Oreos, alternating chocolate and vanilla.Step 2Melt chocolate chips and butter in a medium saucepan over low heat, stirring constantly. Remove from the heat, and whisk in sugars; allow to cool further. Whisk in eggs, one at a time, then add vanilla. Stir in 1 cup cake mix, salt, and 1 cup sprinkles. Step 3Spread mixture on top of Oreos and bake for 45 minutes, until brownies are set in the center and a toothpick comes out clean. Let cool.Step 4Meanwhile, empty frosting into another medium bowl, and stir in remaining 1/2 cup cake mix. Step 5When brownie bars are cool, spread frosting on top, and cover with remaining rainbow sprinkles. Cut into squares.
