5 tbsp. unsalted butter
½ tsp. vanilla extract
2 tsp espresso powder
1¼ tsp. fleur de sel or kosher salt, plus more for sprinkling
1½ cups sugar
¼ cup light corn syrup
¼ cup water
1. Line the bottom and sides of an 8-inch square baking dish with parchment paper. Lightly butter the parchment.
2. In a small saucepan, whisk together the cream, butter, vanilla extract, espresso powder and salt. Heat over medium-high heat and bring to a boil. Remove from the heat and set aside .
3. In a medium saucepan, combine the sugar, corn syrup, and water. Heat over medium-high heat, stirring occasionally with a wooden spoon until the sugar is dissolved. Boil, without stirring until the mixture is a light golden caramel color, swirling the pan every once in a while to prevent burning.
4. Carefully stir the cream mixture into the sugar mixture. Stir carefully and constantly as it will boil up. Clip on a candy thermometer and continue cooking until the mixture registers 248˚ F.
5. Remove from the heat and pour into the prepared pan. Let cool for 30 minutes, then sprinkle with additional salt. Continue to let sit until completely cooled.
6. Cut into 1-inch pieces with a sharp buttered knife or pizza cutter. Wrap the individual caramels in small pieces of wax paper, about 4-inch squares.