Crush the graham crackers into fine crumbs using a food processor or by placing them in a plastic bag and smashing with a rolling pin. Measure out about 1 1/2 cups of crumbs.
Slowly melt the butter in the microwave or on the stovetop until just melted, about 30 seconds in the microwave, until it’s smooth and fragrant.
Pour the melted butter into the graham cracker crumbs and stir until the mixture is evenly coated and resembles wet sand.
Press this crumb mixture firmly into the bottom of your prepared square pan, using the back of a spatula to smooth the surface. Chill in the fridge for about 15 minutes to set.
While the crust chills, combine the caramel bits or chopped candies with the sweetened condensed milk in a microwave-safe bowl. Microwave in 20-second bursts, stirring well after each, until the mixture is smooth, glossy, and oozy, about 1-2 minutes total.
Pour the warm caramel mixture over the chilled crust, spreading it evenly with a spatula. Return the pan to the fridge and chill for another 30 minutes until the caramel is slightly firm but still soft to the touch.
Meanwhile, melt the chocolate chips or melting wafers in a microwave-safe bowl, heating in short 15-second bursts and stirring until smooth, glossy, and fully melted. Let it cool slightly for 2 minutes to prevent cracking.
Pour the melted chocolate evenly over the caramel layer, smoothing it out with a spatula. Sprinkle a pinch of sea salt flakes on top for contrast.
Refrigerate the entire pan for at least 1 hour until the chocolate is fully set and the layers are firm. For an extra crunch, sprinkle chopped nuts on top before the final chill.
Once set, use a sharp knife warmed slightly with hot water to cut into squares, wiping the blade clean between slices for neat, crumb-free edges. Serve straight from the fridge for a firm, chewy bite or let sit at room temperature for 10 minutes for a softer, gooey texture.
