You’ll adore these playful Unicorn Bars — dense, chewy white chocolate blondies studded with colorful sprinkles and finished with a silky buttercream and extra confetti on top. They’re perfect for birthdays, holidays, or any time you want a cheerful treat the kids will request again and again.
These bars started as a beloved bakery tradition for our family at Christmas. I recreated the recipe at home and the result was exactly what my sons remembered: rich, tender blondies with bright sprinkles and a fluffy frosting. Swap the sprinkle colors and icing hues for different seasons — red and green for Christmas, pastels for baby showers, or spookier tones for Halloween — and you’ve got a versatile, crowd-pleasing dessert.
Why you’ll love this recipe
- Simple to make with basic pantry ingredients.
- Highly customizable — change sprinkles and icing colors to fit any occasion.
- Bright, fun, and kid-approved; a guaranteed hit at parties and gatherings.
Notes on key ingredients
The full ingredient amounts are in the recipe card below. A few tips:
- Eggs: Bring to room temperature for better mixing and texture.
- Butter: Use room-temperature butter for both the bars and the frosting.
- White chocolate: Choose a good-quality baking white chocolate for the best flavor.
- Vanilla: Pure vanilla extract improves depth of flavor.
- Sprinkles: Any sprinkles will work; rainbow confetti and assorted shapes create a fun unicorn theme.
Step-by-step instructions
Preheat the oven to 325°F (163°C). Grease a 13 x 9-inch baking pan or line it with parchment paper.
Combine the butter and chopped white chocolate in a saucepan and melt over low heat, stirring occasionally. Remove from heat and let cool for about 10 minutes — the mixture may look slightly separated at first, which is normal and will come together when you add sugar.
Add the granulated sugar and stir until combined. Beat in the eggs one at a time, mixing well after each addition. Stir in the flour, salt, and vanilla until the batter is smooth, then fold in the sprinkles (a mix of flat confetti and small round nonpareils gives a fun texture).
Spread the batter evenly in the prepared pan and bake at 325°F for 30–35 minutes, or until a toothpick inserted near the center comes out clean. Allow the bars to cool completely on a wire rack before frosting.
For the buttercream: Beat 1 cup of room-temperature butter until light and fluffy (about 2 minutes). Gradually add powdered sugar, alternating with the heavy cream (1–2 tablespoons at a time) until you reach a smooth, spreadable consistency. Beat in the vanilla.
Reserve 1/2 cup of the frosting and tint it light turquoise with blue food coloring. Transfer half of the tinted frosting to a separate bowl and add a drop of red to create purple. Adjust coloring as needed for desired shades.
Frost the cooled bars with the remaining white buttercream. Put the blue and purple icings in separate piping bags (or disposable sandwich bags with the corner snipped). Pipe diagonal blue lines across the blondies, then pipe purple lines diagonally in the opposite direction to form a diamond pattern. Finish with extra sprinkles and serve.
Top tips for success
- Use room-temperature butter and eggs for a smoother batter.
- Pure vanilla gives the frosting and bars the best flavor.
- Make sure the bars are completely cool before frosting to prevent melting.
- Wipe your knife between cuts to keep slices neat.
- Customize icing and sprinkle colors to match any theme or holiday.
Storing and freezing
- Store the bars in a single layer in an airtight container in the refrigerator for 3–5 days.
- To freeze, place bars in a single layer between sheets of parchment and store in a freezer-safe container for up to 1–2 months. Thaw in the refrigerator before serving.
Ingredients
Brownie Layer
1 cup butter, softened at room temperature
10 ounces white chocolate, chopped
1 1/4 cups granulated sugar
4 large eggs (room temperature)
2 cups all-purpose flour
1 tablespoon vanilla
1/2 teaspoon salt
1/2 cup rainbow sprinkles
Buttercream Frosting
1 cup butter, softened at room temperature
4 cups powdered sugar
3 tablespoons heavy cream (add more if needed)
Red and blue food coloring
1/2 cup assorted rainbow sprinkles for decorating
Instructions
- Grease a 13 x 9-inch pan or line with parchment paper.
- Preheat oven to 325°F (163°C).
- Melt butter and chopped white chocolate together over low heat, stirring until smooth. Cool 10 minutes.
- Stir in granulated sugar until combined.
- Add eggs one at a time, mixing well after each addition.
- Fold in flour, salt, and vanilla until combined, then stir in sprinkles.
- Spread batter into the prepared pan and bake 30–35 minutes, until a toothpick comes out clean.
- Cool completely on a wire rack.
- Make buttercream by beating butter, then gradually adding powdered sugar and cream until smooth. Stir in vanilla.
- Reserve 1/2 cup frosting and tint it blue; mix half of that with a touch of red to make purple.
- Frost the bars with remaining white icing. Pipe blue and purple lines in crossing diagonal patterns and sprinkle with decorations.