Line your baking dish with parchment paper, leaving some overhang for easy removal, and set aside.
In a mixing bowl, combine the creamy peanut butter, honey, and melted butter. Stir with a spatula until the mixture is smooth, creamy, and slightly sticky, about 2 minutes.
Crush the graham crackers into fine crumbs using a food processor or by placing them in a plastic bag and rolling over them with a rolling pin. Add the crumbs to the peanut butter mixture and stir until evenly coated and thick.
Press the mixture firmly into the prepared baking dish using the back of a spatula or your hands, spreading it out into an even layer. Chill in the fridge for at least 2 hours until firm.
While the base chills, melt the dark chocolate chips in a microwave-safe bowl in 30-second bursts, stirring between each until smooth and glossy.
Remove the chilled base from the fridge and pour the melted chocolate over it, spreading evenly with a spatula to create a smooth, glossy top layer.
Sprinkle a pinch of sea salt flakes over the chocolate for a touch of contrast and flavor.
Refrigerate the bars for another 30 minutes until the chocolate is set and shiny. Once ready, lift the entire block out of the dish using the parchment overhang.
Use a sharp knife to cut the chilled block into 12 even squares, wiping the blade clean between cuts for neat edges.
Serve immediately or store in an airtight container in the fridge for up to a week. These bars are best enjoyed when slightly softened from refrigeration, revealing their sticky, crunchy layers.
