Brush a cookie sheet with a thin layer of vegetable oil. Spread 1 cup pecans in the middle third of a standard cookie sheet leaving a 2 1/2 inch border on the top and bottom of the sheet. (you are essentially forming a square in the center.)
Bring sugar (1 cup), corn syrup (1 tablespoon), butter (1 cup), and bourbon (1/4 cup) to a boil in a heavy saucepan over medium heat, stirring constantly. Cook until mixture is golden brown and a candy thermometer registers 290°F to 310°F (about 15 minutes).
Pour sugar mixture over pecans on a baking sheet. Sprinkle the chocolate chips (1 cup) over the hot toffee. Allow everything to sits for 30 seconds. Chocolate chips will melt. Spread melted chocolate chips evenly over top then sprinkle with remaining 1/2 cup chopped pecans.
Allow cooling for about 1 1/2 hours. Break into chunks. Store in an airtight container.
Notes
Gather all your ingredients before you get started. You probably already do that whenever you cook, but when making candy it's even more important. Once your toffee reaches 290-310°F (143-149°C), you need to immediately remove it from heat, stir well, and pour mixture onto the prepared baking sheet.
Humidity will affect the texture of the finished toffee. Rather than having its signature crispiness, it can be limper or saucy.
Temperature and its dissipationare really important, so use the largest burner of the stove to ensure the sides of the pot heat along with the bottom. Make sure you bring the mixture to a boil over medium heat.
Using a higher heat can easily lead to scorching and burning. You’ll also want to use a strong temperature-neutral spoon to avoid hot spots. A wooden spoon works well but a high temperature rated silicone will do the trick too.
Butter- it’s important to use the real deal butter for this one. Margarine is mainly vegetable oil and light butter tends to contain water, making it lighter on fat and calories.