Adapted from Smitten Kitchen
- 1 cup (2 sticks or 8 ounces) butter
- 1/2 cup light brown sugar
- 1/2 cup white sugar
- 1 1/2 teaspoons molasses (can swap corn syrup or honey)
- 1/4 teaspoon salt (or a heaping 1/4 teaspoon flaky sea salt)
- 1 1/2 teaspoons instant espresso powder
- 1 cup semisweet chocolate chips, or 6 ounces semisweet chocolate, chopped
- 1/2 cup chopped hazelnuts (toasted, skinned and cooled) or another nut of your choice
Line a small (9"x13") baking sheet with parchment paper or a silicone mat and set aside.
In medium heavy saucepan (3 to 4 quarts) with a candy thermometer attached, melt the butter, brown sugar, white sugar, molasses, salt and espresso together. Cook over medium heat, stirring occasionally with a whisk (one that reaches into the corners is especially helpful here) until the temperature approaches 250°F, at which point you should stir constantly until it reaches 300°F.
Pour immediately into the prepared baking sheet—you can spread it more evenly with a offset or silicon spatula, but don't worry if you have neither. Sprinkle the chocolate chips over the toffee and let them sit for a minute until soft, then spread the chocolate evenly over the candy base. Sprinkle the chocolate with chopped hazelnuts; if you want to expedite the cooling process, you can slide the sheet onto a cooling rack in the freezer until the toffee is set.
Break into pieces and store in an airtight container. If your kitchen runs warm, you might prefer to keep it in the fridge so the chocolate doesn't get soft.