Step 1: Preheat and Prepare - Begin by preheating your oven to 350°F (175°C). Grease your 9x13-inch baking pan lightly or line it with parchment paper for easy removal.
Step 2: Mix the Wet Ingredients - In a mixing bowl, combine the melted unsalted butter, large egg, light brown sugar, and vanilla extract. Whisk them together until the mixture is well blended and smooth.
Step 3: Combine the Dry Ingredients - In another bowl, whisk together the all-purpose flour and salt. Gradually add this dry mixture to the wet ingredients, stirring until just combined. Be careful not to overmix; a few lumps are perfectly fine.
Step 4: Fold in the Extras - Gently fold in the chopped graham crackers and semi-sweet chocolate chips. This step adds an incredible texture and flavor to your bars.
Step 5: Pour and Bake - Pour the mixture into the prepared baking pan, spreading it out evenly. Bake in the preheated oven for about 25-30 minutes, or until the edges are golden brown and a toothpick inserted in the center comes out with a few moist crumbs.
Step 6: Create the Gooey Filling - While the bars are baking, prepare the gooey filling. In a saucepan over medium heat, combine the sweetened condensed milk and creamy peanut butter. Stir continuously until the mixture is smooth and heated through. Once the bars are out of the oven, pour the peanut butter mixture over the top and spread it evenly.
Step 7: Final Touches - Return the pan to the oven and bake for an additional 10-15 minutes, just until the top is set and slightly golden. Remove the bars from the oven and let them cool in the pan for at least 15 minutes before slicing into squares.
