Line a 9x9 inch baking dish with parchment paper and preheat oven to 350°F if using nuts. Spread the chopped pecans evenly in the bottom of the dish.

In a heavy-bottom pot, combine sugar, butter, water, and salt. Cook over medium heat, stirring constantly until the mixture reaches 300°F.

Remove from heat and stir in vanilla. Pour hot mixture over pecans in the baking dish.

Sprinkle chocolate chips over the warm mixture and cover to melt for about 4 minutes.

Swirl the melted chocolate into the toffee mixture and sprinkle additional toppings, if desired.

Allow to cool completely at room temperature for about 4 hours or refrigerate to speed up the process.

Once cooled, lift the toffee from the dish using parchment paper and cut into squares or bars.