Kefir butter is a term Bar Tartine uses to describe cream cultured with kefir grains and churned into butter. Kefir grains are opaque, probiotic colonies of lactic acid bacteria, yeast, lipids, sugars, and proteins that turn milk lactose into tangy lactic acid. Uncultured cream may also be used to make butter, but culturing increases its nutritional value and adds layers of tart flavors and aromas. Use the best quality cream you can find for this recipe. After making it, you’ll have both butter and buttermilk—and you can reserve kefir cream as well. Kefir grains are sometimes found at health food stores, and readily available online.
- Glass or plastic container large enough to hold at least 2½ quarts cream
- Butcher string
- Plastic wrap or clean kitchen towel
- Ice, for ice bath
- Small bowl, for ice bath
- Medium bowl, for catching buttermilk
- Stand mixer
- Plastic wrap
- Wax paper or small container with lid, to store butter
- 2 quarts heavy whipping cream
- 1 teaspoon kefir grains
1. Pour cream into large glass or plastic container, allowing space at the top for carbon dioxide production while cream cultures. Wrap kefir grains in cheesecloth, making a loose pouch by tying ends of cloth with butcher string (once cream cultures and thickens, retrieving loose grains without cloth will be difficult). Tuck kefir pouch into cream, resting tied end over side of the bowl. Cover loosely with plastic wrap or towel and let sit at room temperature for 24 to 48 hours.
2. The time required for the cream to culture depends on the temperature of the room in which it’s sitting (72°F is ideal; otherwise, it may take up to 48 hours to culture). Cream is done culturing when it becomes as dense as sour cream or thick yogurt. Don’t worry about its flavor; once the cream is this thick, it has cultured, and will naturally taste as tangy as crème fraîche.
3. Once cream is cultured, remove cheesecloth pouch. (Chef Cortney Burns notes that kefir grains may be re-used forever; to do so, retrieve grains from pouch and place them in a container filled with a pint to a quart of milk and refrigerate. This will put them “to sleep” until you’re ready to use them again. Make sure to change the milk every seven days.)
4. Refrigerate kefir cream for three hours or overnight.*
5. Prepare an ice bath by filling a small bowl with roughly one-quarter ice and the rest water. Place colander over a medium-size bowl and set aside.
6. Add 4 cups kefir cream to the bowl of a stand mixer. Use the machine’s splashguard, or tent the opening between the bowl and top of the machine with plastic wrap. Turn mixer on medium. Once cream begins to froth, turn mixer to high.
7. Watch cream closely, and stop machine once butter has separated from buttermilk, about 4 to 7 minutes. Once separated, butter curds will be about the size of cottage cheese. Pour into a colander lined with cheesecloth and set over a bowl to catch buttermilk.*
8. Next, immerse the butter curds in an ice water bath, squeezing butter mass under ice water to expel more whey. Squeeze until water pressed from the butter runs clear.
9. Remove butter from water and squeeze again to extract remaining liquid. Repeat with remaining cream.
10. Reserve 1 cup of unsalted butter for pound cake, and add salt as desired to remaining butter.
* NOTE: If making Burns’s pound cake, reserve 1 cup cultured cream for the garnish. If making her seeded buttermilk crackers, be sure to save the buttermilk produced during the butter-making process at right; it will keep in the refrigerator for two weeks.