Step 1: To make the toffee filling, add the butter (100g) and sugar to a large nonstick pan. Heat gently until the butter has melted and the sugar has dissolved, then add in your condensed milk, once you add this in bring to a boil and stir continuously.
Step 2: Here you are best to reduce the heat gradually until you start to see the mixture thicken. I have seen plenty of recipes that say it only takes 5 mins, for me, it has always taken a little longer and once you have patience it will form into toffee without burning.
Tips: Toffee can be used for a number of fillings, see my banoffee pie as an example.
