If using nuts, preheat oven to 350 degrees Fahrenheit. Spread nuts on a baking sheet lined with parchment paper and bake in the preheated oven for 10 minutes. This will bring on a crunchier and more flavorful, nuttier experience.
Heat sugar, butter, corn syrup, and salt in a saucepan over medium high heat.
Stir continuously. The mixture will start to golden. We want to get it to a medium-brown shade. If using a candy thermometer, it should reach 290-300 degrees Fahrenheit.
Once it has reached the deep golden color or a temperature of 295 degrees Fahrenheit, remove from heat and carefully add in vanilla. Stir to combine.
Pour the mixture over the toasted nuts (optional) or directly onto a parchment lined baking sheet.
While toffee is cooling, sprinkle chocolate chips on top and let it melt for a few minutes before using a spatula to gently spread it (optional).
Let cool for at least 1 hour at room temperature, or in the fridge until completely cool and hardened.
Once hardened, break into pieces and store in an airtight container.