01 - Preheat oven to 350°F. Line an 8-inch square baking pan with parchment paper.
02 - Combine flour, sugar, salt, and softened butter in a bowl, mixing until crumbly. Press evenly into prepared pan and bake for 15 to 18 minutes until lightly golden. Allow to cool completely.
03 - In a saucepan over medium heat, melt sugar while stirring constantly until amber in color. Add cubed butter and stir until fully melted. Slowly pour in heavy cream (mixture will bubble) and stir until smooth. Fold in vanilla extract and salt. Allow to cool for 5 minutes.
04 - Distribute chopped nuts evenly over cooled base layer. Pour prepared caramel over nuts and spread uniformly. Refrigerate for 30 minutes until firmly set.
05 - Combine chopped chocolate and butter in a heatproof bowl set over simmering water, or microwave in 30-second intervals. Stir until completely smooth.
06 - Pour melted chocolate over caramel layer and spread evenly across surface. Refrigerate for at least 1 hour until fully set.
07 - Remove from baking pan and cut into uniform bars using a sharp knife.