Line a 20cm square cake tin with baking parchment. Place all the ingredients in a large non-stick saucepan and melt slowly, stirring to dissolve the sugar.

Bring to a steady boil and cook, stirring all the time to prevent sticking and burning on the base, for 10-15 minutes or until the mixture reaches 113-115°C on a sugar thermometer.

Remove the pan from the heat and cool for 5 minutes, stirring from time to time. Then beat with a wooden spoon until it becomes very thick and loses its shine - the longer you beat it the more granular it becomes. Creamy fudge is beaten for less time - up to you.

Press the fudge into the prepared tin and smooth flat with a metal spoon. Leave to set and cut into squares.