Prepare the dish by lining a 9×9 inch baking dish with parchment paper and evenly distributing 1 cup of chopped pecans across the bottom.

In a medium-sized pot, combine the butter, granulated sugar, water, and salt. Heat over medium heat, stirring constantly until it liquefies and begins to bubble, about 5 minutes.

Attach a candy thermometer and continue heating until the mixture reaches 300°F, the hard crack stage.

Remove from heat and stir in 1 teaspoon of vanilla extract.

Pour the hot caramel over the layer of pecans and spread evenly.

Sprinkle 1 cup of chocolate chips over the toffee layer and cover to help melt.

Sprinkle additional pecans and flaked sea salt over the melted chocolate.

Allow the toffee to cool completely at room temperature for 4 hours before cutting into pieces.