Line the bottom of a 20-cm (8-inch) square pan with parchment paper, letting the paper hang over two sides for easy unmoulding.
In a saucepan, combine all the ingredients except for the chocolate and vanilla.
Bring to a boil and cook without stirring until a candy thermometer
reads 112 °C (235 °F). Immediately remove from the heat. Add the chocolate and vanilla without
stirring. Let cool for about 15 minutes.
Beat with a wooden spoon for 1 to 2 minutes and pour into the pan. Cool to room temperature. Cut into 25 squares.