Line a 20 x 20cm brownie tin with baking paper. Put the cream, sugar and glucose in a pan. Heat gently, stirring constantly, until the sugar dissolves, then turn up the heat and simmer, stirring regularly, until the temperature reaches 115-117C on a sugar thermometer (the soft ball stage). Take off the heat and stir in the vanilla.
Pour into the lined tin then leave until cool and set. Cut into 50 little squares.