Preheat your oven to 350°F (175°C). Line an 8×8 inch square baking pan with parchment paper, ensuring there is a little overhang on the sides so you can easily lift the bars out later.

In a medium-sized mixing bowl, combine the graham cracker crumbs, melted butter, and granulated sugar. Stir until the mixture resembles wet sand and the crumbs are evenly coated with butter.

Transfer the crumb mixture to the prepared baking pan. Use the bottom of a measuring cup or your fingers to press the mixture firmly and evenly into the bottom of the pan to create a solid crust.

If your peanut butter is stiff, microwave it for 15-20 seconds until it is slightly pourable. Spread the peanut butter evenly over the graham cracker crust, leaving a tiny margin around the edges.

Sprinkle the semi-sweet chocolate chips evenly over the peanut butter layer. Follow this with a dense layer of mini marshmallows. Sprinkle the broken graham cracker pieces and sea salt on top for added texture.

Place the pan in the oven and bake for 20 to 25 minutes. The marshmallows should be puffed up and toasted to a beautiful golden brown. If you prefer them darker, you can broil them for the last 30 seconds, but watch them very closely!

Remove from the oven and let the bars cool completely in the pan on a wire rack. This is the hardest part, but cooling is essential for the layers to set so you can cut clean squares. Once cool, lift the parchment paper to remove the block and slice into 16 bars.