Instructions

• Heat the oven to 350°F. Line a 9-by-13-inch pan with parchment, leaving overhang on two sides.
• Beat the softened butter and sugar until light and creamy. Beat in the egg and vanilla until smooth.
• Whisk the flour, baking powder, and salt in a separate bowl. Add the dry mixture to the butter mixture and stir just until no dry streaks remain.
• Fold in the sprinkles and white chocolate chips. Press the dough evenly into the prepared pan and scatter a few extra sprinkles over the surface.
• Bake for 22 to 25 minutes, until the edges are lightly golden and the center looks set. Cool completely in the pan.
• Lift out the slab, cut it into 24 bars, and pack in a single layer or with parchment between layers for a cookie exchange.