Melt 1/2 lb butter/marg ( I use butter, in for a penny...)in a pint of water in a non-stick pan. (V. important, that bit)
Add (prepare yourself) 4lbs of sugar.
Stir like billy-o so it doesn't catch
Once it's boiling, add the condensed milk, simmer for about 20 mins, keep stirring.
Then (this is where you sweat off some calories in preparation for eating) take off the heat and beat it and beat it and beat it for at least five minutes. You can add flavourings at this stage - vanilla, peppermint, etc if wanted.
Chuck it in a greased tin, and if you want it in regular shapes, cut it when it's partly cooled.
Enjoy. Your arms will hurt for near a year, though.
And you'll gain a stone.
1 can of devil's brew (I think it's about 400g but I can't check as we are, temporarily, depleted)