St. Patricks Rainbow Cookie Bars (Printable Version)

Buttery bars filled with white chocolate chips and colorful sprinkles for a festive St. Patricks treat.

# Needed Ingredients:

→ Dry Ingredients

01 - 2 cups all-purpose flour
02 - 1/2 teaspoon baking powder
03 - 1/4 teaspoon salt

→ Wet Ingredients

04 - 3/4 cup unsalted butter, melted and cooled
05 - 1 cup granulated sugar
06 - 1/2 cup light brown sugar, packed
07 - 2 large eggs
08 - 2 teaspoons pure vanilla extract

→ Mix-Ins

09 - 3/4 cup white chocolate chips
10 - 1/2 cup rainbow sprinkles, divided

# Steps:

01 - Preheat oven to 350°F. Line a 9x9-inch baking pan with parchment paper, leaving overhang for easy removal.
02 - In a medium bowl, whisk together flour, baking powder, and salt. Set aside.
03 - In a large bowl, whisk melted butter, granulated sugar, and brown sugar until smooth. Add eggs and vanilla extract; whisk until fully combined.
04 - Gradually fold dry ingredients into wet ingredients using a spatula, mixing until just combined.
05 - Stir in white chocolate chips and 1/3 cup of rainbow sprinkles.
06 - Spread batter evenly into prepared pan. Sprinkle remaining sprinkles over the top.
07 - Bake for 25-28 minutes, or until edges are golden and a toothpick inserted into center comes out mostly clean.
08 - Cool completely in the pan on a wire rack before slicing into bars.

# Expert Advice:

01 -
  • They come together in under an hour, which means you can actually pull off something impressive on a weeknight or last-minute gathering.
  • The buttery shortbread base stays soft inside with crispy edges, and that's the perfect texture combination nobody ever gets tired of.
  • White chocolate and sprinkles turn an ordinary bar cookie into something that feels intentional and celebratory without requiring any fancy techniques.
02 -
  • Cooling completely is everything—I learned this the hard way by slicing too early and ending up with crumbly pieces instead of actual bars, and it changed everything once I waited.
  • The melted butter must cool slightly before mixing with eggs, or you'll scramble your eggs and end up with a weird texture that no amount of other ingredients can fix.
  • Don't skip dividing the sprinkles; folding some into the batter creates delightful surprises in each bite while the top layer guarantees everyone sees the festive intention.
03 -
  • Line your pan with parchment paper with an overhang on all sides so you can lift the entire baked slab out and cut bars on a cutting board instead of wrestling inside the pan.
  • If your sprinkles bleed color into the batter, it's actually kind of beautiful and totally normal—gel-based sprinkles bleed less if that bothers you, but the regular ones taste better.
  • Room temperature eggs and cooled melted butter make a measurable difference in how smoothly everything combines, so plan a few minutes ahead if you want to do this right.
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