Buy reduced price cream to make cheap as chips butter
Put the cream into a bowl
Whisk it until you get peaks
Whisk some more
When the cream has separated into a liquid and a solid -STOP
Put the solid into a muslin cloth or clean tea towel and squeeze out the remaining liquid
Run the butter (solid) under COLD water
Squeeze out excess water
Season with salt if using
Shape and wrap in greaseproof
The liquid you have left in the bowl is buttermilk which is great to use in baking - You can just pour the cream into a clean jar . Screw on the lid and shake , shake , shake until it separates , then rinse as above . Children will love making it this way