Brownies
Preheat your oven to 350°F. Line the bottom of an 8-inch round pan with parchment paper, then grease the sides with oil, dust them with cocoa powder, or use cooking spray. Set aside.
In a medium-sized bowl, sift the dry ingredients together and set aside. Using a large bowl of a stand mixer, beat the sugar and melted butter until the sugar is fully dissolved, around 2-3 minutes at medium-high speed. Let cool before adding the eggs.
Add egg, yolk, vanilla extract, and food coloring, and beat until everything is mixed. Incorporate the dry ingredients into the wet ingredients and mix at low speed until just combined. Do not overbeat. Use a spatula to fold in the chocolate chips.
Pour batter into the prepared baking pan and bake for 35-40 minutes, or until a toothpick inserted in the middle comes out with a few crumbs. Let cool for 20 minutes in the pan, then transfer to a wire rack to cool completely. Start making the frosting while the brownies cool down.
Frosting
Over a large mixing bowl of an electric mixer, (or using a hand mixer) cream the butter at medium speed for 3 minutes, until light and fluffy. Incorporate the cream cheese and beat for an extra minute.
Add the sifted powdered sugar, vanilla extract, and salt to the cream cheese mixture and mix for an extra 1-2 minutes, until light and fluffy. Do not overbeat.
Cut the brownies into 12 equally sized slices. Using a piping bag, and Wilton tips 103, 104, 1A, and 1M, pipe each slice separately. Add your favorite sprinkles and enjoy!