- Butter a 20-inch (8-inch) square pan. Line with parchment paper, letting the paper hang over two sides.
- In a saucepan, bring the sugar, syrup, and water to a boil. Cook until the mixture turns a caramel colour.
- Remove from the heat. Gradually add the cream and butter. Stir to combine. Bring to boil and cook until a candy thermometer reads 117 °C (242 °F). Remove immediately from the heat and add the chocolate. Let stand for 1 minute. With a spatula, combine without incorporating any air, until smooth.
- Pour into the prepared pan. Let cool. Cover and let cool completely in the refrigerator, about 2 hours.
- Unmould and cut the caramel into cubes. Let it warm up, if needed, to facilitate cutting.
Wrap each caramel in a square of parchment paper and place them side-by-side on sheets of parchment paper and layer them in an airtight container.
For an extra chocolate version with fleur de sel, melt and temper milk or dark chocolate. Dip the caramel squares in the tempered chocolate, one at a time, using a fork. Let set on a sheet of parchment paper and drop a few grains of fleur de sel just before the chocolate sets up.