Cosmic blondies

Get ready to elevate your dessert game with these cosmic blondies. Inspired by the classic American grocery store staple, these treats feature a decadent, brown butter base topped with a mesmerizing, marbled ganache that looks like it came straight from a galaxy.

This recipe is as fun to make as it is to eat. The brown butter and salt create a rich, savory foundation, while the customizable nature of the base means you can fold in your favorite mix-ins like toasted nuts or sprinkles. While the swirled ganache might seem like a technical challenge, a little confidence and a steady hand with a spatula are all you need to create a stunning, professional-looking finish.

Quick Details

• Total Time: 2 hours (1 hour baking, 1 hour cooling)
• Yield: 24 servings

Ingredients

For the Blondies

• 1 cup/227 grams unsalted butter (plus more for greasing)
• 2 ice cubes
• 1 tablespoon vanilla extract
• 2 2/3 cups/340 grams all-purpose flour
• 1 teaspoon baking soda
• 1 teaspoon kosher salt (or 1/2 teaspoon fine salt)
• 1 cup/220 grams dark brown sugar
• 1/2 cup/100 grams granulated sugar
• 2 large eggs
• 3/4 cup/113 grams chopped semisweet chocolate chunks or chips
• 3/4 cup/113 grams mini M&Ms

For the Ganache

• 1/2 cup/120 milliliters heavy cream
• 12 ounces/340 grams chopped white chocolate
• Pinch of salt
• 2 food colorings (gel paste preferred)
• Sanding sugar (optional)
• Flaky sea salt (for finishing)

Instructions

1. Prep: Heat your oven to 350 degrees. Butter a 9-by-13-inch metal baking pan and line it with parchment paper, leaving an overhang on the long sides to serve as handles for easy removal.

2. Brown the Butter: Melt butter in a medium saucepan over medium heat. Continue cooking until it foams and develops toasty brown flecks. Remove from heat, stir in the ice cubes (careful of the bubbling!), and add the vanilla extract. Set aside.

3. Mix the Base: Whisk flour, baking soda, and salt in a medium bowl. In a large bowl, whisk your sugars with the brown butter mixture until smooth, then add the eggs one at a time, whisking heartily after each.

4. Fold and Bake: Gradually stir the flour mixture into the sugar base, then fold in the chocolate. Spread into your pan and bake for 22 to 24 minutes. For an extra-chewy texture, gently tap the pan on your counter once it leaves the oven. Let cool completely.

5. Create the Galaxy: Heat heavy cream until steaming, remove from heat, and whisk in the white chocolate and salt until smooth. Divide the ganache into three portions: leave one plain and tint the others with your food coloring. Dollop the ganache across the blondies and use an offset spatula to swirl the colors together. Finish with sanding sugar and flaky sea salt. Allow to set for 30 minutes at room temperature or 15 minutes in the fridge.

Expert Tips

• Use authentic white chocolate—check labels for cocoa butter—instead of baking chips to prevent the ganache from seizing.
• For the best visual effect, choose colors that won't turn muddy if they mix (e.g., pink/purple or red/blue). Avoid mixing contrasting colors like blue and orange.
• A little goes a long way with gel coloring, so start small!

Store any leftovers in an airtight container at room temperature for up to 3 days. Find more inspiration at the original source.