Prepare the Baking Sheet:

Line a baking sheet with parchment paper or a silicone baking mat. Set aside.

Make the Toffee:

In a medium saucepan over medium heat, melt the butter.

Add the granulated sugar and salt, stirring constantly until the sugar is dissolved.

Attach a candy thermometer to the saucepan and cook the mixture, stirring constantly, until it reaches 300°F (hard crack stage). This should take about 10-15 minutes.

Once the toffee reaches 300°F, remove the saucepan from heat and stir in the vanilla extract.

Spread the Toffee:

Quickly pour the hot toffee onto the prepared baking sheet, spreading it out evenly with a wooden spoon or silicone spatula.

Add the Chocolate:

Immediately sprinkle the semi-sweet chocolate chips over the hot toffee. Let them sit for a minute to soften, then spread the melted chocolate evenly over the toffee using a spatula.

Top with Nuts:

Sprinkle the chopped nuts evenly over the melted chocolate.

Cool and Break the Toffee:

Let the toffee cool completely at room temperature or in the refrigerator until the chocolate is set.

Once the toffee is completely cool and set, use a knife to break it into pieces.