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These frosted sugar cookie cake bars are a dream — they capture the flavor of classic frosted sugar cookies in a soft, chewy bar. Thick buttercream frosting and a pillowy cookie base make them perfect for celebrations or an everyday treat.
I’m excited to share this recipe — I tested it until the texture was just right. These bars are soft with a slight chew, full of sweet vanilla flavor, and finished with a generous layer of buttercream. They’re easy to customize: change the frosting color and sprinkles to match any theme or holiday.
The cookie base texture was inspired by my s’mores bars. I adapted that method to create a tender, slightly dense base that holds up well under a thick frosting. While the bars are excellent without frosting, the buttercream really elevates them and gives them that classic sugar cookie vibe.
Why You’ll Love These Sugar Cookie Cake Bars
- They look festive and cheerful — perfect for birthdays, showers, or holidays. The frosting color and sprinkles are fully customizable.
- If you enjoy soft, thick sugar cookies, you’ll love the rich, tender texture of these bars.
- The buttercream frosting has a classic birthday-cake feel that complements the cookie base beautifully.
Ingredient Notes and Substitutions
- Gluten free flour blend: Use a 1:1 gluten-free blend that contains xanthan gum for best results. If you don’t need gluten free, substitute regular all-purpose flour in the same amount.
- Brown sugar: Light brown sugar gives a subtle caramel note, but dark brown sugar works fine if that’s what you have.
- Egg replacer: This recipe uses an egg replacer to make the bars eggless. Follow the package directions when preparing it. If you prefer, you can use 1 large egg instead.
- Powdered sugar: Any brand is fine; sift only if it’s lumpy.
- Gel food coloring: Gel coloring provides a more concentrated color without thinning the frosting. Use sparingly for pastel shades.
Step-By-Step Instructions
STEP ONE: Cream the butter with the granulated and brown sugar until smooth. The brown sugar adds flavor and chew.
STEP TWO: Mix in the egg replacer (prepared per package instructions) and vanilla extract until incorporated.
STEP THREE: Whisk the dry ingredients together, then add them to the wet mixture and mix on low until combined.
STEP FOUR: Press the dough evenly into a parchment-lined square pan. You can use your hands to press it in for an even layer. Bake at 350°F (175°C) for about 16–18 minutes, until the edges are lightly golden. Let the pan cool completely before removing.
STEP FIVE: Make the buttercream: beat the butter until creamy, add the powdered sugar, then add whole milk one tablespoon at a time until you reach the desired consistency. Add gel food coloring if desired and mix to blend. Spread the frosting over the cooled bars, then slice.
Expert Tips
- Weigh your flour for best accuracy — this recipe needs 222 grams of flour if you measure by weight.
- If your frosting is too thick, thin it with more milk a teaspoon at a time. If it becomes too thin, add powdered sugar a tablespoon at a time until it firms up.
- To get a soft pastel shade, pick up a tiny amount of gel food coloring on a toothpick and mix it in gradually.
- Make sure the bars are completely cool before frosting so the buttercream doesn’t melt.
Frequently Asked Questions
They are done when the edges are set and have a light golden color. The center will be set but still soft.
Yes. Substitute non-dairy butter and your preferred plant-based milk for the butter and whole milk in the frosting.
Natural colorings can work, though they may produce more muted tones than gel colors. Experiment with small amounts to achieve the shade you want.
How To Store
Store the frosted bars in an airtight container at room temperature for up to 2 days. After that, keep them refrigerated and consume within 5 days total for best texture and freshness.
Did you make these frosted sugar cookie cake bars? Leave a comment or tag @justastastyblog on Instagram and use #justastastyblog. Subscribe to get new recipes in your inbox.
📖 Recipe
The Best Frosted Sugar Cookie Cake Bars
Ingredients
For the cookie bars:
- 1 ½ cups (222g) gluten free flour blend
- 1 ½ teaspoons baking powder
- ¼ teaspoon salt
- ½ cup (113g) unsalted butter room temperature
- ½ cup (100g) granulated sugar
- ½ cup (100g) light brown sugar packed
- 1 tablespoon egg replacer mixed with 2 tablespoons water
- 1 teaspoon vanilla extract
For the buttercream frosting:
- ½ cup (113g) unsalted butter room temperature
- 1 ½ cups (180g) powdered sugar
- 1-2 tablespoons whole milk
- food coloring optional
Instructions
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Preheat oven to 350°F. Line a square baking pan with parchment paper and set aside.
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In a small bowl, whisk the flour, baking powder, and salt together and set aside.
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Using a hand mixer or stand mixer fitted with a paddle, cream the butter with both sugars until combined. Add the prepared egg replacer and vanilla extract and beat until smooth.
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Add the dry ingredients and mix on low until just combined. Press the dough into the prepared pan and bake for 16–18 minutes, until the edges are slightly browned. Cool completely before removing from pan.
To make the buttercream frosting:
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Beat the butter until smooth. Gradually add powdered sugar and beat until combined.
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Add milk one tablespoon at a time until you reach the desired consistency. Stir in gel food coloring if using. Spread the frosting over the cooled cookie base, then slice into bars.
Notes
- If you don’t need a gluten free version, use all-purpose flour instead.
- Follow the egg replacer package instructions; after mixing with water, it needs a few minutes to thicken before using.
- If you prefer, 1 whole egg can replace the egg replacer in this recipe.
- If the frosting becomes too thin, add more powdered sugar a tablespoon at a time to thicken it.
