Ingredients
2500ml double cream
1 tsp flaked sea salt

Method
Ideally you should use a stand mixer but if you do not have one then a hand mixer would work - or you can do this by hand, you will just be there for some time and will feel like Popeye at the end.

Put the cream into a your stand mixture and set it mixing over a medium heat and keep mixing.  Your cream will turn into beautifully whipped cream and then after a few mins the solid and liquid will separate and you will have butter and buttercream.

Get a muslin cloth and line a colander over a bowl.  Poor the butter and butter milk into the cloth and leave to drain.  Once the buttermilk has drained off, gather the muslin and start to twist to ensure that you have all of the buttermilk drained. Put the buttermilk into a container and keep in the fridge.

Get a large bowl of cold water and with your butter still in the muslin cloth, wash the butter and squeeze through the cloth, this washes the butter and washes off the sour buttermilk.  Get clean iced water and repeat this process.  Keep repeating until the water no longer turns cloudy.

Put the butter into clingfilm and manipulate into a log shape. Put into the fridge.