You can find sweet cream butter at any grocery store or farmer's market, but whey butter is more difficult to find because of its limited appeal. Whey butter has a strong, salty taste reminiscent of cheese and can be more oily than creamy. It is, however, one good way of using the whey that remains after the cheesemaking process and can provide a different type of flavor and texture as a spread on breads and crackers.
Separate the whey from the solids created during the cheese making process and allow the whey to cool. Use the solids in another recipe or process.
Skim the cream from the water by running the whey through a cream separator. This will ensure the sweetest possible butter as well as the highest fat butter possible from your whey. Home cream separators are several hundred dollars and make sense for those who plan on making many batches of butter over a long period of time.
Chill the cream that you've separated out of the whey. Use the remaining liquid for another recipe or discard.
Beat the cream in a standing mixture on medium speed until bubbles begin to form on the surface. Turn the speed to high and beat the cream until it solidifies. Press the butter between two plates lined with paper towels overnight. Wrap the butter and store in the fridge.