1-Preheat and prepare the pan: Start by preheating your oven to 350°F (175°C) and lining an 8×8-inch baking pan with foil or parchment paper, then spray it with nonstick cooking spray for easy removal later.

2-Make the fudge filling: Melt together 1 1/4 cups chocolate chips, 1/3 cup sweetened condensed milk, and 1 tablespoon unsalted butter over low heat until it’s smooth and glossy. Set it aside to cool while you work on the blondie batter, which includes mixing 1 stick (about 113 grams) of melted unsalted butter with 1 cup light brown sugar, 1 large egg, and 1 teaspoon vanilla extract until smooth.

3-Build the blondies: Next, stir in 1/8 teaspoon salt and 1 cup all-purpose flour until just combined don’t overmix to keep the texture light. Spread half of this batter evenly in your prepared pan, then add flattened pieces of the cooled fudge filling on top for that gooey chocolate center.

4-Cover and bake: Cover it with the remaining batter, smoothing it out so the fudge stays tucked inside. Pop it in the oven and bake for 25 minutes until the top is lightly golden, but remember to pull it out while the center is still fudgy for the best results.

5-Finishing touches: Let the blondies cool completely before slicing; this helps them firm up without getting dense. Total time is around 35 minutes, including prep and baking, so it’s quick enough for a weeknight treat. For extra tips, check out this no-fail blondies recipe for more ideas on perfecting your bake.

6-Avoid overbaking: Avoid overbaking since the blondies firm up as they cool, and always measure ingredients accurately to prevent a dense texture. Using a metal pan ensures even heat distribution, making your fudge stuffed blondies come out just right.