Birthday Cake Blondies

Birthday Cake Blondies with Cream Cheese Frosting

These Birthday Cake Blondiesare like a birthday party in every bite, chewy, rich, and loaded with melty white chocolate chips and rainbow sprinkles. Topped with a silky vanilla bean cream cheese frosting, they’re the ultimate treat for celebrations, bake sales, or just a little weekday joy. Whether you’re new to baking or a seasoned home baker, this easy recipe walks you through every step and explains the why behind the ingredients, so your blondies turn out perfect every time.

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Ingredient Breakdown (and Why They Matter)

For the Blondies:

• ½ cup unsalted butter (melted) Melted butter creates a soft, chewy blondie with that rich, almost caramelized flavor. Unsalted allows you to control the salt content.

• 1 cup brown sugar Brown sugar adds moisture and chew, thanks to its molasses content. It also brings a warm, deep sweetness that complements the white chocolate beautifully.

• 2 eggs (room temperature) Eggs bind everything together and provide structure and richness. Room temp eggs mix more evenly into batter, preventing a dense texture.

• 1 tbsp vanilla extract This boosts the overall flavor with a warm, sweet aroma. Don’t skimp, vanilla rounds out the entire dessert.

• 1 cup all-purpose flour Provides structure. Just the right amount keeps the blondies soft, not cakey.

• ¼ tsp baking powder Adds a subtle lift to keep the blondies from being too dense.

• ½ tsp salt Balances the sweetness and enhances the flavors. A small amount makes a big difference.

• 1 cup white chocolate chips Sweet and creamy, white chocolate melts into the batter for rich pockets of flavor.

• 4 tbsp rainbow sprinkles Adds fun color, texture, and whimsy! Use “jimmies” style sprinkles, they melt better into batter without bleeding.

For the Frosting:

• ¼ cup softened unsalted butter Acts as a creamy base for the frosting, rich and smooth.

• 2 tbsp softened cream cheese Adds a tangy balance to the sweetness and gives the frosting structure.

• 1 ½ cups powdered sugar Sweetens and thickens the frosting to a smooth, spreadable consistency.

• ¼ tsp salt Cuts the sweetness and enhances flavor, yes, even in frosting!

• 1 tsp vanilla bean paste Brings a stronger, richer vanilla flavor with gorgeous specks. Vanilla extract works just as well if that’s what you have.

• 1 tbsp milk Thins the frosting slightly for that perfect creamy spreadability.

Storage & Make-Ahead Tips

• Room Temperature: Store frosted blondies in an airtight container for up to 2 days.

• Fridge: Lasts up to 5 days chilled. Let them sit at room temp for 10 minutes before eating.

• Freezing: Freeze unfrosted blondies (whole or sliced) wrapped tightly for up to 2 months. Thaw overnight in the fridge and frost before serving.