Prepare Your Baking Pan: Preheat your oven to 350°F (175°C). Grease a 9×9-inch baking pan with non-stick spray or line it with parchment paper for easy removal. Make sure the parchment overhangs slightly on the sides to create “handles” for lifting the bars out later.

Cream the Butter and Sugar: In a large mixing bowl, use a hand or stand mixer to beat the butter and sugar on medium-high speed until light and fluffy. This should take about 2 minutes. The creaming process is crucial as it incorporates air into the mixture, creating a soft and tender texture in the finished bars.

Add the Wet Ingredients: Crack in the egg, then pour in the vanilla extract and almond extract. Beat on low speed until everything is fully incorporated. The batter should appear smooth and slightly glossy.

Incorporate the Dry Ingredients: In a separate bowl, whisk together the flour, baking powder, and salt. Gradually add the dry mixture to the wet ingredients, mixing on low speed until a soft, slightly sticky dough forms. Avoid overmixing, as it can make the bars dense.

Add the Sprinkles: Gently fold in the sprinkles with a spatula. Be careful not to overmix to avoid the colors bleeding into the dough.

Press and Bake: Transfer the dough to your prepared baking pan. Use the back of a spoon or a small offset spatula to press it evenly into the pan. Bake in the preheated oven for about 20 minutes. The edges should appear slightly golden, and the center will look slightly underbaked. This ensures the sugar cookie bars stay gooey and soft as they cool.

Cool Completely: Remove the pan from the oven and place it on a wire rack to cool for about 30 minutes. Wait until the sugar cookie bars are fully cooled before icing to prevent the frosting from melting.

Cream the Butter: In a medium-sized mixing bowl, beat the butter with a hand or stand mixer until smooth and creamy. This step eliminates any lumps and ensures a silky icing texture.

Add the Sugar and Vanilla: Gradually add the powdered sugar, ½ cup at a time, beating well after each addition. Once all the sugar is incorporated, pour in the vanilla extract and beat again to combine.

Adjust the Consistency: Add the milk, one tablespoon at a time, beating on low speed after each addition. The icing should be thick yet spreadable. If it’s too thick, add a little more milk; if it’s too thin, mix in a bit more powdered sugar.

Frost the Bars: Use a spatula or offset knife to spread the icing evenly over the cooled sugar cookie bars. For an extra festive touch, sprinkle additional rainbow sprinkles on top while the icing is still wet to ensure they stick.

Slice and Serve: Allow the icing to set for about 15 minutes before lifting the sugar cookie bars out of the pan using the parchment paper handles. Slice into even squares or rectangles with a sharp knife, wiping the blade clean between cuts for neat edges. Enjoy your perfectly soft and chewy sugar cookie bars!