01 - Preheat oven to 350°F. Line an 8-inch square baking pan with parchment paper.
02 - In a mixing bowl, combine flour, sugar, salt, and softened butter until mixture resembles coarse crumbs. Press evenly into prepared pan. Bake for 15 to 18 minutes until lightly golden. Remove and allow to cool completely.
03 - In a saucepan over medium heat, melt sugar while stirring constantly until amber in color. Add butter and stir until fully melted. Slowly pour in heavy cream, stirring continuously as mixture will bubble vigorously. Mix until smooth consistency. Stir in vanilla extract and salt. Let cool for 5 minutes.
04 - Distribute chopped nuts evenly over cooled base layer. Pour prepared caramel over nuts and spread evenly across surface. Refrigerate for 30 minutes until caramel is fully set.
05 - Combine chopped chocolate and butter in a heatproof bowl. Melt using either double boiler method or microwave in 30-second intervals, stirring between bursts until smooth.
06 - Pour melted chocolate over caramel layer and spread evenly to all edges. Refrigerate for at least 1 hour until chocolate is completely set and hardened.
07 - Remove assembled bars from baking pan. Using a sharp knife, cut into 16 equal bars.