Spray a 9-inch square baking dish with cooking spray and line with parchment paper.
Spread the chopped pecans in a single layer on top of the parchment.
Add butter, sugar, and salt to a heavy bottomed 3-quart pot.
Bring to a boil, over medium low heat, stirring frequently to dissolve the sugar.
Once the candy is boiling, stir occasionally, slowly and evenly, until the candy has reached 290°F to 300°F, or “hard crack”, on a candy thermometer.
Once the candy has reached 290°F – 300°F, remove from heat and gently stir in the vanilla extract.
Carefully pour the mixture over the chopped pecans.
Let the candy sit for a few minutes, undisturbed, before sprinkling the chocolate chips over the top.
Cover the baking dish with foil and let sit for 5 minutes or until the chocolate has softened.
Remove the foil and gently spread the softened chocolate into an even layer; an offset spatula works best for this.
Place the candy in the refrigerator and let cool completely; give it at least 2 hours.
Lift the parchment out of the baking dish and place the toffee on a cutting board or solid surface.
Use a knife to gently break it into smaller pieces.
Store in an airtight container in a cool place.
