1. Prepare the Crust:

1. Line a baking sheet with parchment paper and set aside.
2. In a heavy saucepan, melt butter over medium heat. Add sugar and salt, stirring constantly until mixture comes to a boil.
3. Continue cooking, stirring frequently, until mixture reaches 300°F (hard crack stage) and turns a golden amber color, about 10-12 minutes.
4. Remove from heat and immediately stir in vanilla extract. Pour onto prepared baking sheet and spread evenly.
5. Sprinkle chocolate chips over hot toffee and let sit for 2-3 minutes until softened. Spread chocolate evenly over toffee layer.
6. Sprinkle with chopped nuts and toffee bits while chocolate is still soft. Let cool completely at room temperature or refrigerate until set.
7. Break into pieces and store in an airtight container.