Ingredients:

  • 1 cup (2 sticks) unsalted butter, cut into 1-inch cubes
  • 1 cup granulated sugar
  • 1/4 cup water
  • 1 Tablespoon light corn syrup or golden syrup
  • 1/2 teaspoon fine sea salt
  • 8 ounces dark chocolate (60-70% cocoa), finely chopped or chips
  • 1/2 teaspoon flaky sea salt (such as Maldon), for finishing

Instructions:

  1. Prep the Pan: Line the 9x13 inch baking sheet with a silicone mat or lightly oiled parchment paper. Set aside.
  2. Chop Chocolate: Finely chop the chocolate (if not using chips) and place it in a bowl so it is ready to use immediately once the toffee is poured.
  3. Combine Ingredients: In a heavy-bottomed saucepan, combine the butter, granulated sugar, water, corn syrup, and fine sea salt.
  4. Melt and Dissolve: Heat the mixture over medium-low heat. Stir constantly until the butter is fully melted and the sugar is completely dissolved. Do not let the mixture boil before the sugar is dissolved.
  5. Wipe the Sides (Crucial Step): Once boiling begins, stop stirring. Use a pastry brush dipped in warm water to gently wash down any sugar crystals clinging to the sides of the pan. This prevents crystallization.
  6. Increase Heat and Monitor: Clip the candy thermometer to the side of the pan. Increase the heat to medium.
  7. Cook to Temperature: Allow the mixture to boil steadily, without stirring. Cook until the thermometer reads exactly 300°F (149°C) (Hard Crack Stage). This takes approximately 15–20 minutes.
  8. Remove Immediately: As soon as 300°F is reached, remove the pan from the heat immediately.
  9. Pour and Spread: Quickly and carefully pour the hot toffee mixture onto the prepared baking sheet. Gently tilt the pan to spread the toffee into an even layer, about 1/4 inch thick. Do not scrape the bottom of the pan.
  10. Add Chocolate: Wait about 1 minute until the toffee is slightly set. Sprinkle the chopped chocolate evenly over the hot surface. Let stand for 3–5 minutes until the chocolate melts.
  11. Spread: Use an offset spatula to gently spread the melted chocolate over the entire toffee surface.
  12. Season: Immediately sprinkle the flaky sea salt evenly over the melted chocolate.
  13. Chill: Transfer the tray to the refrigerator and chill until completely set and brittle—about 60–90 minutes.
  14. Break: Once firm, lift the toffee off the tray. Break the large slab into irregular, rustic pieces using a heavy knife or blunt edge.