Place the cream, maple syrup, brown sugar, sugar, corn syrup and salt in a heavy-bottomed saucepan and bring to a boil, stirring until the sugar dissolves. Set a candy thermometer in the centre of the saucepan (for example, hanging off a wooden spoon) and simmer over medium heat, without stirring, until the thermometer reads 110°C (230°F). Remove from the heat. Add the chocolate and vanilla but do not stir.
