Step by step

Method

4 steps

1. 1

   Heat the oven to 350°F. Grease a 9×13-inch pan (or line with parchment with overhang for easy lift-out). Cream 1 cup softened unsalted butter with 1½ cups sugar until light and fluffy, 2–3 minutes. Beat in 2 large eggs and 2 teaspoons vanilla until smooth.

2. 2

   Whisk 2½ cups all-purpose flour, 1 teaspoon baking powder, and ½ teaspoon salt. Stir the dry mix into the butter mixture just until no flour streaks remain — don't overmix or the bars turn tough. Press the dough into an even layer in the pan.

3. 3

   Bake 22–26 minutes until the edges are lightly golden and the center looks set (a toothpick should come out with a few moist crumbs, not wet batter). Cool completely in the pan — frosting on a warm bar will melt into a puddle.

4. 4

   Beat ½ cup butter, 2 cups powdered sugar, 2 tablespoons milk, and 1 teaspoon vanilla until fluffy. Spread over the cooled bars, add sprinkles, and cut into squares. You want soft, chewy cookie bars under a sweet frosting — not dry crumbly edges or a raw doughy middle.