Ingredients
Equipment
Method
Prep the pan and oven
- Preheat the oven to 350°F and line an 8x8 baking pan with parchment paper. Make sure the parchment overhangs so you can lift the blondies out later.
Mix the blondie batter
- Whisk melted butter and brown sugar together until smooth. Keep whisking until no sugar lumps remain.
- Add the large egg, egg yolk, and vanilla extract, then whisk until glossy. The mixture should look thicker and smoother than before.
- Stir in all-purpose flour, baking powder, and salt until just combined. Stop as soon as you don’t see dry flour, and avoid overmixing.
Fold in the mix-ins
- Fold in the red, white, and blue M&Ms, red and blue star sprinkles, and white chocolate chips. Fold gently so the sprinkles and chips stay evenly distributed.
Bake
- Spread the batter evenly into the prepared pan and scatter extra star sprinkles on top. Use a spatula to level the surface for even baking.
- Bake at 350°F for 22–25 minutes until the top is golden and set but the center still has a very slight jiggle. Look for edges that feel set while the middle barely moves when nudged.
Cool and cut
- Cool completely in the pan before cutting into squares. The blondies firm up as they cool, so slices will cleanly hold their shape.
Notes
Pro tip: underbake slightly—when the center has a gentle jiggle and the top is golden, you’ll get thick, chewy blondies instead of cakey squares. Store airtight at room temperature for up to 3 days or refrigerate up to 5 days. Freeze baked and cooled blondies for up to 2 months; thaw overnight in the fridge. For a simpler swap, use a 1:1 gluten-free all-purpose flour blend to make them gluten-free (check that it contains xanthan gum for best chew).