Stir the sugar and milk together in a heavy-bottomed pot, then cover and heat slowly until it starts to boil.

Add the rest of the ingredients, except for the vanilla extract and stir.Put the lid back on the pot.

Boil gently at a low setting, stirring occasionally for about 15 minutes. The mixture will turn a golden-brown colour.  If you have a cooking thermometer, cook the mixture until it reaches 117°C (242°F). If you don't have a thermometer, after 10 -12 minutes, drop a teaspoon of mixture into a dish of cold water. It should set and the lump should be soft and not hold its round shape when you scoop it out of the water.

Take the fudge off the heat and stir in the vanilla extract. Leave with the lid on to cool until the thermometer reads about 80°C (175°F).  This will take about 15 minutes.

Beat the fudge with an electric mixer for at least 5 minutes, until it thickens.

Pour into a greaseproof paper lined baking dish that is about 20cm x 20cm (8 in x 8 in) in size.

Leave to set. When set, cut into small squares or rectangles.