Prepare your 9x9 inch baking dish by lining it with parchment paper, leaving overhang for easy removal later. Preheat your oven to 350°F if toasting pecans.

Spread 1 cup of chopped pecans evenly in the lined dish. If not toasted yet, place in preheated oven for 5-7 minutes until fragrant and slightly golden.

In a medium pot, combine 1 cup of butter, 1 cup of granulated sugar, 1/4 cup of water, and 1/2 teaspoon of salt. Stir over medium heat until butter melts.

Attach a candy thermometer and continue stirring, aiming for the hard crack stage at 300°F, which can take about 10-15 minutes.

Once at 300°F, carefully remove from heat and stir in 1 teaspoon of vanilla extract.

Quickly pour the hot caramel over toasted pecans, spreading evenly with a spatula. Allow to sit for about 2 minutes.

While warm, sprinkle chocolate chips over the hot toffee layer. Cover the dish temporarily for about 4 minutes until chocolate melts.

Gently swirl the melted chocolate using a spatula or knife for a decorative finish. Optionally, sprinkle some chopped pecans and flaked sea salt on top.

Let the toffee cool completely at room temperature for about 4 hours or refrigerate for 1-2 hours until firm.

Once fully cooled, lift the toffee out using the parchment, place on a cutting board and slice into pieces.