📖 Instructions

1. Preheat your oven to 375°F (190°C). Grab a 9x13 inch baking pan and line it with parchment paper, leaving an overhang on the sides. This little trick makes it super easy to lift the entire batch of bars out later. Grease the parchment paper lightly with cooking spray or butter.
2. In a large mixing bowl, using an electric mixer (handheld or stand mixer will do the trick), cream together the softened unsalted butter and granulated sugar until the mixture is light and fluffy. This usually takes about 2-3 minutes. Don't skimp on this step; proper creaming incorporates air, which contributes to the cookies' light texture.
3. Beat in the egg and the vanilla extract. Make sure to scrape down the sides of the bowl with a spatula to ensure everything is well combined. You want a smooth, homogenous mixture here.
4. In a separate medium bowl, whisk together the all-purpose flour, baking powder, and salt. Give it a good whisk to evenly distribute the baking powder and salt throughout the flour.
5. Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined. Be careful not to overmix; overmixing can lead to tough cookies, and we're aiming for tender, melt-in-your-mouth goodness. Stop mixing as soon as you no longer see streaks of dry flour.
6. Press the cookie dough evenly into the prepared 9x13 inch baking pan. You can use your hands, a spatula, or even the bottom of a glass to get it nice and flat. Make sure the dough is spread right to the edges of the pan for an even bake.
7. Bake for 15-20 minutes, or until the edges are lightly golden brown and a toothpick inserted into the center comes out clean. Keep an eye on it; ovens vary! The center might look slightly underdone, but it will continue to cook as it cools.
8. Let the cookie bars cool completely in the pan on a wire rack. This is crucial! Trying to frost warm cookies will result in a melty mess, and no one wants that.
9. While the bars are cooling, prepare the frosting. In a medium bowl, beat the softened butter until creamy, about 1-2 minutes. Gradually add the powdered sugar, one cup at a time, beating until smooth after each addition. If the frosting seems too thick, add milk or cream one teaspoon at a time until you reach your desired consistency. Beat in the vanilla extract.
10. Once the cookie bars are completely cool, lift them out of the pan using the parchment paper overhang. Spread the prepared frosting evenly over the top of the cookie bars. A small offset spatula works wonders for this, but a butter knife or the back of a spoon will work too.
11. Now for the fun part: decorate with festive Easter sprinkles! Be generous! Slice into squares or rectangles and serve. These bars store well in an airtight container at room temperature for up to 3 days, or in the fridge for up to a week.