Line a baking sheet with parchment paper and set aside.

In a saucepan over medium heat, combine butter, sugar, corn syrup, and salt.

Stir continuously until the mixture comes to a boil.

Attach a candy thermometer and cook until the mixture reaches 300°F (hard crack stage).

Remove from heat and stir in vanilla extract.

Quickly pour the toffee onto the prepared baking sheet, spreading it evenly.

Let it cool for about 5 minutes.

Sprinkle chocolate chips over the warm toffee and let sit for a few minutes to melt.

Spread the melted chocolate evenly and sprinkle with chopped nuts if desired.

Allow the toffee to cool completely at room temperature until hardened.

Break into pieces and store in an airtight container.