1 liter whipping cream
1 pinch of starter culture or 1 dl. buttermilk
3-5 gram salt (½-1 tsp)

Ice cubes
½ dl. vegetable oil (grape/rape/olives/thistle/walnut/peanut)

Bowl
Electric whisk

Add starter culture or buttermilk to the cream and mix thoroughly. Cover and ferment the cream for approximately 24 hours at room temperature. If the room temperature is above 24°C - reduce fermentation time slightly. After fermenting the cream, refrigiate it. The ideal temperature for the cream is 10°C during summertime and 15°C during wintertime.

• Gently whisk the chilled fermented cream until whipped cream forms. Keep whisking as it begins to seperates into butter and buttermilk. The longer you fermented the cream for, the faster this happens. You ususally need to whisk it for about 3-4 minutes but it depends on the creams temperature and how intensely you whisk it. Whisk until there seems to be equal parts of buttermilk and butter in the bowl (1liter cream yields almost 4 dl buttermilk)
  
  
• Drain the buttermilk out and replace it with the same amount of very cold water. and eventually a number of ice cubes. Whisk for another 3-4 minutes.
  Adding cold water helps to extract more buttermilk from the butter. This process must be repeated a few times until no more buttermilk drains off.
  
  
• Queeze out the last bits of water from the butter by kneading it with your hands or stirring thoroughly with a spoon.
  
  
• Add salt to taste and mix well, either by kneading or stirring with a spoon. 
  
  
• To make a soft spreadable butter, add a little good quality oil, e.g. rapeseed, grapeseed, olive oil etc. (optional)

Save til initially drained buttermilk - this is genuine buttermilk. You may drink it or use it as a starter for other home made dairy products. Or include it in home made baked goods.