Prepare Your Baking Sheet
Line a baking sheet with parchment paper or a silicone baking mat and set it aside.
Make the Toffee
In a heavy-bottomed saucepan, melt the butter over medium heat. Add the sugar and salt, stirring constantly.
Bring the mixture to a boil, continuing to stir to prevent burning. Attach a candy thermometer and cook until the mixture reaches 290°F (soft crack stage).
Remove the saucepan from heat and quickly stir in the vanilla extract.
Pour and Spread
Pour the hot toffee mixture onto the prepared baking sheet, spreading it out evenly with a spatula. Work quickly, as the toffee will harden fast.
Add Chocolate and Nuts
Sprinkle the chocolate chips evenly over the hot toffee. Wait a minute or two for the heat to melt the chocolate.
Use a small spatula to spread the melted chocolate into a smooth layer.
Immediately sprinkle the chopped nuts over the top of the chocolate.
Cool and Break
Allow the toffee to cool completely at room temperature or in the refrigerator until hardened.
Once set, break the toffee into bite-sized pieces using your hands or a knife.