put the sugar, water, condensed milk, butter and syrup into a large pot (this is to prevent it boiling over)

heat gently allowing the sugar to dissolve

raise to 115° Celsius and keep it boiling for about 30 minutes until it caramelizes and thickens

do not let the fudge get above 118° Celsius

watch the bubbles change and when they are big in the middle you are at the fudge stage

check this by dropping a small amount into water – it should for a soft ball

remove from the heat and stir in the vanilla and vinegar

beat the fudge with an electric beater on a low speed to avoid splash backs which can result in bad burns (use lavender essential oil on a burn straight away to prevent blisters)

do this until the colour lightens and it has thickened and it has started crystallizing against the side of the pot

pour into a lined rectangular dish and cool until firm enough to cut into squares (about 20 minutes)

allow to stand for 1 hour before removing from the dish