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These cake batter bars are my go-to for birthdays potlucks and anytime I want a thick bar with the ultimate fudgy bite. Each one is soft in the middle and piled high with swirls of buttery vanilla frosting plus festive bursts of sprinkles in every bite. If you crave a bakery-style dessert without fuss these bars never let you down.
I first baked these bars late one night when my daughter could not sleep and wanted to help in the kitchen. Now she calls them her happy bars and requests them for every celebration and lazy weekend.
Ingredients
- Butter: Softened gives richness and structure to both the bars and the buttercream. Choose high-fat European style butter if you want a truly luscious crumb.
- White Sugar: creates sweetness with a gentle caramel undertone when creamed with butter. Use fine granulated for the smoothest mix.
- Egg and Egg Yolk: add moisture chew and a golden hue. Fresh large eggs work best.
- Vanilla Extract: brings that essential cake batter taste. Real vanilla makes a big difference in this recipe.
- All Purpose Flour: forms the foundation for sturdy but tender bars. Measure by whisking then sweeping a cup for accuracy.
- Salt: highlights flavor and balances the sweetness. I use kosher salt for a gentle salty note.
- Baking Powder and Baking Soda: both work together to create the perfect lift and fluffy crumb.
- Cornstarch: a secret weapon for softness and melt-in-your-mouth texture.
- White Chocolate Chips: melt into creamy pockets for extra indulgence. Use high-quality chips for better flavor.
- Rainbow Sprinkles: not only add color they give a slight crunch and real birthday cake spirit.
- Confectioners Sugar: makes a cloudlike vanilla buttercream. Sift it if lumpy.
- Milk: loosens the buttercream to spreadable bliss. Whole milk adds extra richness.
- Salt in buttercream: balances out the sweetness. Add a pinch at a time and taste as you go.
Step-by-Step Instructions
- Make the Bar Dough:
- Cream the softened butter with sugar using a hand mixer or sturdy spoon for about two to three minutes until light and fluffy. This aerates the mix so your bars have a tender crumb. Beat in the whole egg egg yolk and vanilla extract until glossy and combined.
- Combine the Dry Ingredients:
- In a separate bowl whisk together all purpose flour salt baking powder baking soda and cornstarch. Mix thoroughly so you do not get any clumps of leavening in the bars.
- Mix the Dough:
- Gradually add the dry ingredients to the wet mixture in batches stirring just until the mixture is no longer dusty. Be careful not to overwork it or the bars can turn dense.
- Add Sprinkles and Chocolate Chips:
- Fold in the sprinkles and white chocolate chips using a gentle hand to keep the batter tender.
- Pan and Bake:
- Press the dough evenly into a foil lined 9x9 pan using greased hands for even thickness. Bake at three hundred fifty degrees Fahrenheit for about twenty five to twenty eight minutes. Look for a lightly golden top and slightly set edges. Let the bars cool completely in the pan.
- Prepare Vanilla Buttercream:
- While the bars cool cream the softened butter until creamy and smooth. Add milk and vanilla extract and beat until fluffy. Gradually add the confectioners sugar and mix until a soft spreadable frosting forms. Taste and add a pinch of salt if needed.
- Frost and Decorate:
- Spread the buttercream over the cooled bars using an offset spatula for even swirls. Scatter extra sprinkles across the top for color and fun. Slice into generous squares and serve.
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The vanilla extract is my favorite ingredient here. I once splurged on a bottle of real vanilla from Mexico and I swear it made these bars unforgettable. One time my son snuck extra sprinkles into the batch and we have kept the tradition ever since.
Storage Tips
Once the frosting is set cover the bars tightly in the pan or transfer to an airtight container. They keep fresh at room temperature for two days or in the refrigerator for up to five days. For longer storage freeze individual bars wrapped in plastic then thaw at room temperature.
Ingredient Substitutions
If you want to lighten things up swap half the butter for Greek yogurt or unsweetened applesauce. For a nutty option try adding a handful of chopped pecans or walnuts with the chips. Use chocolate or butterscotch chips instead of white chocolate if that is what you have.
Serving Suggestions
These bars are showstoppers for birthday parties or bake sales. For a more decadent treat serve chilled with a scoop of ice cream or with a drizzle of melted chocolate on top. My family loves them with strawberries and whipped cream for a dessert twist.
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Cultural and Historical Context
Cake batter flavored desserts are rooted in American birthday celebrations and bake sale nostalgia. The rainbow sprinkles give a nod to childhood favorites while the buttercream is inspired by classic layer cakes. These bars pack everything you love about a frosted celebration cake into a portable satisfying treat.
Recipe FAQs
- → How do I make the bars extra fudgy?
For extra fudgy bars, avoid overmixing once you add the dry ingredients and watch closely so you don't overbake. Pull them from the oven when the edges are set but the center is still slightly soft.
- → Can I use different types of sprinkles?
Jimmies or confetti sprinkles work best because they won’t bleed color as much as nonpareils during baking, keeping the bars vibrant and festive.
- → Should the bars cool before frosting?
Yes, let the bars cool completely in the pan before spreading on the buttercream. This prevents the frosting from melting and sliding off.
- → What’s the best way to store them?
Store the bars covered at room temperature for up to 2 days, or refrigerate for longer freshness. Bring to room temperature before serving for best texture.
- → Can I freeze these bars?
The bars freeze well. Wrap tightly and freeze up to 2 months. Thaw overnight in the fridge, then enjoy as desired.