Crumble the stock cubes into the bottom of your saucepan or slow cooker.
Add ham hock, butter beans and chopped tomatoes.
Add hot water (I use about a pint, but you can adjust this depending on how thick you like your soup. You need enough to dissolve your stock cubes but after that it's up to you). Stir in the tomato puree.
Leave it to simmer, stirring occasionally. If you're using a slow cooker you can leave it as long as you want (I cook mine 8 hours or overnight). If you're using a saucepan, 30 to 45 minutes should be enough.
Check that the ham is piping hot then serve with crusty bread.