1 jar of Marshmallow Fluff (available in most good sweetshops like Bean in Tunbridge Wells but some supermarkets stock it too)
1lb 4oz caster sugar (yes really)
1 small can of evaporated milk
3/4 teaspoon of salt
3/4 teaspoon of vanilla essence
12oz plain chocolate, broken into pieces
Have the chocolate all broken into pieces, the vanilla & a well buttered 9*9 inch tin ready to hand.
Use a spatula or similar to scoop all of the Marshmallow Fluff into a large saucepan, if it's your first time it takes quite some time to get the stuff out of the jar. Throw in the sugar, butter, evaporated milk & salt. Combine over a very low heat stirring constantly. If you start getting very large brown specks come up to the surface the heat is too high &/or you are not stirring enough.
While still constantly stirring bring the mixture to the boil slowly, it can be quite difficult to tell if the mixture has reached boiling point because the stirring creates pockets of air which bubble to the surface. Every now & then stop stirring for a few seconds, if the bubbling continues then the mixture is boiling. Boil for 5 minutes.
Take the mixture off the heat & pour in the chocolate & the vanilla essence. Again stir constantly & briskly until all the chocolate has melted & the mixture is smooth. Tip into the buttered baking tin as quickly as you can before it sets into the saucepan.
Leave it to set until cool.