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Frosted vanilla sprinkle sugar bars cut into squares on a marble board with rainbow jimmies scattered on top.

Soft Vanilla Sprinkle Sugar Bars with Buttercream

Thick sugar cookie dough studded with sprinkles, baked in one pan, then topped with vanilla buttercream and more sprinkles.
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Prep Time 15 minutes
Cook Time 27 minutes
Total Time 1 hour 42 minutes
Servings: 16 servings
Course: Dessert
Cuisine: American
Calories: 401
Ingredients Method Notes

Ingredients
  

Sugar Cookie Bars
  • 230 g unsalted butter, softened (1 cup)
  • 300 g granulated sugar (1 1/2 cups)
  • 2 large eggs room temperature
  • 2 tsp vanilla extract
  • 375 g all-purpose flour (3 cups); spooned and leveled
  • 1 tsp baking powder
  • 1/2 tsp salt
  • 65 g rainbow sprinkles (jimmies) (1/3 cup); not nonpareils
Vanilla Buttercream
  • 115 g unsalted butter, softened (1/2 cup)
  • 300 g powdered sugar (2 1/2 cups); sifted if clumpy
  • 1 tsp vanilla extract
  • 2 whole milk to 3 tbsp
  • 2 tbsp rainbow sprinkles for topping

Method
 

Make the Sugar Cookie Bars
  1. Heat the oven to 175 C / 350 F. Grease a 9x13-inch (33x23 cm) baking pan and line it with parchment, leaving a little overhang on the long sides.
  2. Beat the softened butter and granulated sugar together for 2 to 3 minutes, until pale and fluffy.
  3. Add the eggs one at a time, beating well after each. Mix in the vanilla extract.
  4. Whisk the flour, baking powder, and salt together in a separate bowl. Add to the butter mixture in two additions, mixing on low just until combined.
  5. Fold in the sprinkles by hand with a spatula. Stir gently so the color doesn't bleed into the dough.
  6. Press the dough evenly into the pan with a greased spatula or your fingers, pushing it into the corners.
  7. Bake for 25 to 28 minutes, until the edges are golden and a toothpick in the center comes out with a few moist crumbs, not wet batter.
  8. Cool the bars completely in the pan on a wire rack, about 60 minutes. Don't frost while they're warm or the buttercream will melt into the dough.
Frost and Finish
  1. Beat the softened butter for the frosting until smooth, about 1 minute.
  2. Add the powdered sugar in two batches, beating on low first, then increasing speed once it's incorporated.
  3. Beat in the vanilla extract and 2 tablespoons of milk. Add the extra tablespoon of milk only if the frosting is too thick to spread.
  4. Spread the buttercream evenly over the cooled bars with an offset spatula, then scatter the remaining sprinkles over the top.
  5. Chill for 15 minutes to set the frosting, then lift the bars out using the parchment overhang and cut into 16 squares.

Notes

  • Cool the bars fully before frosting or the buttercream melts into the dough.
  • Use jimmies, not nonpareils, so the sprinkles keep their color in the oven.
  • Don't overmix once the flour goes in or the bars turn tough.
  • Line the pan with parchment and leave an overhang for easy lifting.