📖 Instructions

1. Before you do anything, preheat your oven to 350°F (175°C). Seriously, don't skip this; a properly preheated oven is key to even baking! Grab a 9x13 inch baking pan and either line it with parchment paper, leaving an overhang on the sides for easy lifting, or spray it really well with non-stick cooking spray. If you're using parchment, a little spray underneath helps it stay put.
2. In a large mixing bowl, combine the all-purpose flour, baking powder, and a pinch of salt. Use a whisk to really get them mixed together. This ensures your leavening agents are evenly distributed, so your cookies rise beautifully. Set this bowl aside for a moment.
3. In a separate, even larger bowl (or the bowl of your stand mixer fitted with the paddle attachment), beat together the softened unsalted butter and granulated sugar until it's light and fluffy. This usually takes about 2-3 minutes on medium-high speed. You'll notice the color lighten and the texture become airy. This creaming process incorporates air, making your bars tender.
4. Now, add the large eggs, one at a time, beating well after each addition. Scrape down the sides of the bowl as needed to make sure everything is getting incorporated. Then, stir in the vanilla extract. Don't be shy with the vanilla, it's the heart of a good sugar cookie!
5. Gradually add the dry ingredient mixture to the wet ingredients, mixing on low speed until *just* combined. And I mean just combined! Overmixing will develop the gluten too much, resulting in tough, dry cookie bars, and nobody wants that. Stop as soon as you see no more streaks of flour.
6. Press the dough evenly into your prepared 9x13 inch baking pan. You can use your hands, a spatula, or even the bottom of a glass sprayed with non-stick spray to get a nice, even layer. Make sure it's spread from edge to edge so all the bars bake consistently.
7. Bake for 20-25 minutes, or until the edges are lightly golden brown and a wooden skewer or toothpick inserted into the center comes out clean or with a few moist crumbs attached. The center might still look a *tiny* bit soft, and that's okay, it means they'll be wonderfully chewy. Don't overbake! Overbaked sugar cookies are sad sugar cookies.
8. Once baked, remove the pan from the oven and let the cookie bars cool completely on a wire rack. This is *super* important before frosting. If you try to frost warm cookies, your frosting will melt and slide right off, turning into a pastel puddle. Patience is a virtue here, friend!
9. While the bars cool, prepare your festive frosting! In a medium mixing bowl (or a stand mixer), beat the softened unsalted butter until it's light and creamy, about 1-2 minutes. Gradually add the powdered sugar, one cup at a time, beating well after each addition. This prevents a powdered sugar cloud from erupting in your kitchen!
10. Once all the powdered sugar is incorporated, add the milk (start with 2 tablespoons and add more if needed, a teaspoon at a time) and the vanilla extract. Beat on medium-high speed until the frosting is smooth and fluffy, about 3-5 minutes. It should be light, airy, and spreadable. If it's too thick, add a tiny bit more milk; if too thin, a bit more powdered sugar.
11. Now for the fun part: add a few drops of gel food coloring to achieve your desired pastel shades. You can divide the frosting into smaller bowls to make multiple colors, or simply color the whole batch one lovely spring hue. Pink, blue, yellow, green – mix and match! Mix well until the color is evenly distributed.
12. Once the cookie bars are completely cool, spread the frosting evenly over the top using an offset spatula or the back of a spoon. Be generous! Finish by showering your frosted bars with colorful Easter sprinkles. The more, the merrier, I say!
13. Using the parchment paper overhang (if you used it), carefully lift the entire slab of frosted cookie bars out of the pan and transfer it to a cutting board. This makes cutting so much easier. Use a sharp knife to cut the bars into squares or rectangles of your desired size. Wipe the knife clean between cuts for nice, neat edges. Serve immediately and watch them disappear! Store any leftovers in an airtight container at room temperature for up to 3 days, or in the fridge if you prefer.