Step-by-Step Instructions
1. Prep the Pan & Oven
Preheat your oven to 350°F (175°C). Line an 8×8-inch metal baking pan with parchment paper, leaving an overhang on the sides for easy removal later.
2. Brown the Butter
In a small saucepan over medium heat, melt the butter. Continue cooking, swirling occasionally. The butter will foam, crackle, and then begin to turn a golden-brown color with a nutty aroma (about 3–5 minutes). Immediately pour into a mixing bowl and let it cool for 5 minutes.
3. Mix the Wet Ingredients
Whisk the packed brown sugar into the warm brown butter until smooth. Add the egg, egg yolk, and vanilla extract. Whisk vigorously for about 1 minute until the mixture becomes glossy, thick, and slightly pale.
4. Combine Dry & Wet
In a small bowl, stir together the all-purpose flour, graham cracker crumbs, baking powder, and salt. Fold the dry ingredients into the butter mixture using a rubber spatula just until combined. Do not overmix.
5. Fold & Layer
Fold in half of the mini marshmallows, half of the chopped chocolate, and all of the broken graham cracker pieces. Spread the thick batter evenly into your prepared baking pan. Scatter the remaining marshmallows and chocolate evenly across the top, pressing them slightly into the batter.
6. Bake to Perfection
Bake for 22–26 minutes. The edges should be golden brown and set, while the center remains slightly soft. The marshmallows on top will turn toasted and puffed.
7. Cool & Slice
Allow the blondies to cool completely in the pan on a wire rack for at least 1 to 2 hours before slicing. This resting period allows the melty center and warm marshmallows to set into clean, chewable squares.
Baker’s Pro-Tips
Chef’s Note for Clean Slices: To get razor-sharp cuts without the marshmallows sticking to your blade, wipe your knife with a warm, damp cloth between every slice, or place the cooled pan in the fridge for 15 minutes prior to cutting
