To begin, place the milk and butter in a deep heavy-bottomed saucepan over a medium heat and bring to the boil
Remove from the heat and quickly add the sugar. Return to the heat and when the sugar has completely dissolved, add the condensed milk
Return the whole mixture to the boil then turn down the heat and reduce to a simmer. Keep stirring to prevent the mixture from catching on the bottom of the pan
Cook for 10–15 minutes, or until golden in colour
Remove from the heat and beat with a spoon until the mixture thickens, then pour into a lined 20cm square tray or shallow baking tin, and leave to set. Cut into squares to serve
