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a slice of sugar cookie bar on a plate with chocolate frosting and sprinkles on top, with a bite taken out.
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Chocolate Frosted Sugar Cookie Bars

Chocolate Frosted Sugar Cookie Bars are perfectly soft and chewy, with a thick layer of homemade chocolate fudge frosting, all topped with rainbow sprinkles. These bars come together in no time for a super quick and easy crowd-pleasing treat.
Course Dessert
Cuisine American
Prep Time 25 minutes
Cook Time 30 minutes
Total Time 55 minutes
Servings 9 large bars or 16 smaller bars
Author Tessa Arias

Ingredients

For the cookie bars:

  • 1 ½ sticks (170 grams) unsalted butter
  • 1 cup + 2 tablespoons (225 grams) granulated sugar
  • 2 eggs plus 1 egg yolk, at room temperature
  • 1 tablespoon vanilla extract
  • 2 cups (254 grams) all-purpose flour*
  • 1 ½ teaspoons baking powder
  • 1/2 teaspoon fine sea salt

For the chocolate frosting:

  • 1 1/2 sticks (170 grams) unsalted butter, at room temperature
  • 1 1/4 cups (156 grams) powdered sugar, sifted
  • 1/3 cup (28 grams) cocoa powder, sifted
  • 3 tablespoons heavy cream
  • 1 teaspoon vanilla extract
  • 1/8 teaspoon salt
  • Rainbow sprinkles, to decorate

Instructions

  • Preheat the oven to 350°F. Line a light-colored metal 8x8-inch baking pan with parchment paper leaving an overhang.
  • Place the butter in a large microwave-safe bowl and microwave on 50% power until melted. Alternatively, melt in a medium saucepan on the stovetop. Whisk in the sugar. Let cool to just warm before whisking in the eggs, egg yolk, and vanilla until smooth. Stir in the flour, baking powder, and salt until just combined.
  • Use a spatula to press the dough evenly into the pan.
  • Bake for about 30-35 minutes, or until lightly golden brown on top and the center springs back when lightly pressed. Place the pan on a wire rack and let cool completely. The center may sink slightly as they cool.

To make the frosting:

  • In the bowl of a stand mixer fitted with the paddle attachment, beat the butter on medium-high speed until creamy, about 2 minutes. Scrape down the bottom and sides of the bowl.
  • On low speed, add the powdered sugar, cocoa powder, cream, vanilla, and salt. Scrape down the bottom and sides of the bowl. Increase speed to high and beat for 3 minutes, or until light and fluffy.
  • Remove the cooled bars from the pan using the overhang. Frost with a thick layer of frosting. Sprinkle with sprinkles before cutting into squares. Serve or store in an airtight container at room temperature for up to 2 days or in the fridge for up to 5 days.

Notes

*Be sure to measure your flour accurately. Use a digital kitchen scale or the ‘spoon and level’ method to avoid accidentally adding too much flour, causing hard, dry, or cakey cookie bars.