1. Prepare a baking sheet by lining it with parchment paper or a silicone baking mat, then set aside.

2. In a heavy-bottomed saucepan, combine the butter, granulated sugar, brown sugar, salt, and water.

3. Cook over medium heat, stirring constantly until the mixture reaches 300°F (hard crack stage) on a candy thermometer.

4. Remove the pan from heat and immediately stir in the vanilla extract.

5. Pour the hot toffee mixture onto the prepared baking sheet and spread it evenly with a heat-resistant spatula.

6. Sprinkle the chocolate chips over the hot toffee, letting them sit for a minute until melted.

7. Once the chocolate has melted, spread it evenly over the toffee.

8. If desired, sprinkle chopped nuts over the melted chocolate.

9. Allow the toffee to cool and set for about 2 hours or until the chocolate has hardened.

10. Break into pieces and enjoy!

For a nut-free version, simply omit the walnuts or pecans. You can also sprinkle a pinch of flaky sea salt on top for a salted toffee twist. If you’re feeling adventurous, try adding a bit of espresso powder to the chocolate for a mocha flavor, or substitute the semisweet chocolate chips with white chocolate or a flavored variety like dark or milk for a different taste profile. If you’d like to make a festive version, consider adding some crushed peppermint on top during the holidays.