Line an 8x8 pan with tin foil, allowing the edges to hang over sides. Spray foil with nonstick spray.
Place 15 crackers in the bottom of the pan in 3 rows of five. Sprinkle 1/2 of the peanut butter chips over crackers.
In a small saucepan melt butter and brown sugar over medium heat, stirring constantly, until bubbly and creamy caramel forms, about 4 minutes.
Pour half of the caramel over peanut butter chips and crackers. Add another layer of 15 crackers, top with peanut butter chips, then pour remaining caramel over. Top with another layer of 15 crackers then spread melted chocolate over. Sprinkle with sea salt.
Notes
To melt the chocolate chips, place in a microwave-safe container and microwave in 20-second bursts, stirring between each burst, until smooth and melted. Do not overheat.From Bakergirl