Preheat your oven to 350°F and line a 9x13-inch baking pan with parchment paper so cleanup is basically nonexistent. I always rub a tiny bit of butter on the pan first so the parchment actually stays put instead of peeling up everywhere.

In a large bowl, cream together the softened butter and granulated sugar for about 2-3 minutes using a hand mixer or electric mixer. You want it to look pale and fluffy, like clouds. When you scrape the sides, it should feel light and whipped.

Add the 2 eggs one at a time, beating well after each one so they actually incorporate instead of sitting in little puddles. Then pour in the vanilla extract and mix until smooth. Trust me, this step prevents weird streaks in your confetti blondies family 4th july.

In a separate bowl, whisk together the flour, baking powder, and salt so there are no lumps hiding anywhere. Gently fold this dry mixture into the wet ingredients, alternating with the milk so nothing stays clumpy. Start with half the flour mixture, then half the milk, then the remaining flour and milk—this old-school method works every time.

Fold in the white chocolate chips carefully so they don't break apart, then add the rainbow sprinkles at the very last second. I mean literally right before pouring into the pan, because if you mix them in too early, they start bleeding their colors into the batter and it gets kinda muddy looking.

Pour the batter into your prepared pan and spread it out evenly with a spatula. Bake for 28-32 minutes until the top looks set but still has a tiny jiggle in the center when you shake it gently. Don't overbake or you'll end up with dry bars, which defeats the whole purpose of making these in the first place.

Let the pan cool on the counter for at least 15 minutes before cutting because the bars will be too soft to handle right out of the oven. My kitchen always smells amazing when these are cooling, and that's when I know I should've made a double batch.