In a bowl, combine graham cracker crumbs and melted butter. Stir until fully combined, then press firmly into a parchment-lined baking dish to form the base.

1. In a saucepan, combine sweetened condensed milk, brown sugar, corn syrup, and butter. Cook over medium heat, stirring constantly until thickened and golden (about 8–10 minutes). Remove from heat and stir in vanilla extract.
2. Pour the caramel mixture over the crust, spreading evenly. Let cool slightly.
3. Melt chocolate chips in a microwave-safe bowl or double boiler until smooth. Stir in crisped rice cereal or crushed cornflakes.
4. Pour the chocolate mixture over the caramel layer, spreading evenly.
5. Sprinkle with sea salt if desired.
6. Chill in the refrigerator for 1–2 hours until fully set.
7. Once firm, cut into bars and serve.