Preheat oven to 350.
Soften butter by zapping it in the microwave or leaving it on the counter to get to room temp.
In a large mixing bowl (or stand mixer), add in softened butter, egg, and vanilla extract.
Mix well with a hand mixer or directly in a stand mixer. If the butter is softened enough, it should take a minute or two. If not, you may need to mix a little longer. You want it to be as smooth as possible.
Fold in brown sugar and flour. Mix again really well until a thick, sticky cookie dough forms.
Sprinkle in rainbow / Funfetti sprinkles. At this point, you may want to use a spatula (spray first to help with sticking) to do the final mixing to create the cookie dough.
Grease/line a brownie pan (8x8) and press the dough evenly throughout. I used my hands here! It does not need to be perfect because it will spread in the oven but do your best. Add more sprinkles on top and any other chocolate candy you wish!
Bake for 20 minutes. Let cool for 10 -15 minutes before removing from pan and cutting. Cut to whatever desired size you want! Usually cut 4 times through both vertical and horizontal to make 16 blondies!
Enjoy warm or store on the counter or fridge (in an air-tight container) for 3-4 days.
16 servings