1-First Step: Preparation and Preheating. Start by preheating your oven to 350°F (175°C). While the oven heats, thoroughly grease a 9×13-inch baking pan with butter or cooking spray. For easy removal, you can also line the pan with parchment paper, leaving an overhang on the sides to create “handles” that will help you lift the bars out later. This is especially helpful when frosting them, as it keeps everything contained and neat.

2-Second Step: Creaming the Butter and Sugar. In a large mixing bowl, beat 1 cup of softened butter with 1 cup of granulated sugar until the mixture is light and fluffy. This should take about 2 minutes using a hand mixer on medium speed or 3-4 minutes by hand. The creaming process is crucial because it incorporates air into the mixture, which helps create a lighter, more tender texture in your finished bars.

3-Third Step: Adding Wet Ingredients. Add 1 egg and 2 teaspoons of vanilla extract to the creamed butter and sugar mixture. Beat well until fully incorporated, scraping down the sides of the bowl as needed. The mixture should be smooth and uniform in color at this point. This step ensures that your vanilla flavor is distributed evenly throughout the bars.

4-Fourth Step: Incorporating Dry Ingredients. In a separate bowl, whisk together 2 ½ cups of all-purpose flour, ½ teaspoon of baking powder, and ½ teaspoon of salt. Gradually add this dry mixture to the wet ingredients, mixing on low speed or by hand just until combined. Be careful not to overmix at this stage, as overworking the dough can develop too much gluten and result in tougher bars.

5-Fifth Step: Spreading and Baking. Transfer the dough to your prepared 9×13-inch pan. Using an offset spatula or the back of a spoon, spread the dough evenly across the pan. The dough will be thick, so take your time to create an even layer. Bake in the preheated oven for 18-22 minutes, or until the edges are lightly golden and the center is set. Avoid overbaking when done, the bars should still feel slightly soft to the touch in the center.

6-Sixth Step: Cooling Completely. Remove the pan from the oven and place it on a wire rack to cool completely. This step is crucial if you frost the bars while they’re still warm, the frosting will melt and become runny. Allow at least 1-2 hours for the bars to cool completely, or speed up the process by placing the pan in the refrigerator for about 30 minutes once it has cooled to room temperature.

7-Seventh Step: Preparing the Frosting. While the bars cool, prepare the frosting. In a medium bowl, beat ½ cup of softened butter until smooth and creamy. Gradually add 2 cups of powdered sugar, mixing well after each addition to avoid creating a cloud of sugar dust. Add 2 tablespoons of milk and 1 teaspoon of vanilla extract, then beat until the frosting is smooth and spreadable. If desired, add a few drops of food coloring to achieve your preferred hue.

8-Final Step: Frosting, Chilling, and Serving. Once the bars are completely cool, spread the frosting evenly over the surface using an offset spatula. If you’d like, add sprinkles on top of the frosting while it’s still fresh so they adhere well. Place the pan in the refrigerator for about 30 minutes to allow the frosting to set. Once set, cut the bars into squares you should get about 24 bars from a 9×13-inch pan. Serve at room temperature for the softest texture.