Okay, first — oven to 350°F. That’s your warm-up.

Now grab a 9x13-inch pan and line it with foil. Let the edges hang off like handles — trust me, you'll thank yourself later when it's time to lift the whole thing out. Give it a solid coat of nonstick spray. No “just a mist” business. Corners too.

Melt your butter (microwave, stovetop, whatever works). Pour it into a big bowl and whisk in the sugar. It'll look glossy and a little like you're about to make candy — that’s good.

Now crack in the eggs, add the vanilla and salt, and whisk again until it’s all one big happy mixture.

Add your flour last, and stir gently — like you're folding in a secret. Don’t go overboard here. Overmixing is how bars turn into bricks.

Toss in the sprinkles. Stir just enough to spread the joy around. If the colors start to swirl or smear, pause — you’re stirring too much.

Spread that gorgeous, speckled batter into your pan. It's thick — that's normal. Use a spatula to nudge it into the corners.

Bake for 25 to 30 minutes. The edges should be golden, but the center might look like it’s not quite ready. Here’s the trick: trust the process. These bars keep cooking as they cool.

Let them sit in the pan until fully cooled. Walk away if you have to — temptation is real.

While the bars cool, beat your room-temp butter in a bowl until it looks creamy and soft, like a butter sculpture halfway through creation.

Slowly mix in powdered sugar. Go slow unless you want to sneeze sugar.

Add a couple tablespoons of milk. Mix again. Still too thick? Add a touch more. Then tint it with a drop or two of blue food coloring — stir until it looks like a pastel sky.

If you want those beautiful piped swirls like in the pics, double your frosting. No judgment.

Spread or pipe your buttercream over the cooled bars. Let it be thick. Fluffy. Slightly excessive.

Then — the finale — rain down more sprinkles. Don’t be shy.

Use those foil edges to lift the whole thing out in one go. Then slice into as many bars as your heart (or event) desires.