Kefir is a fermented dairy product similar to drinkable yogurt. It doesn't require specialized equipment or much work to maintain, and once you acquire a culture it can be kept going indefinitely – for free, if you surreptitiously feed it from your dining hall's milk machines. If you can't sneak milk, buying a gallon from the store is still much, much cheaper than buying good kefir or yogurt.

Basic Method

• Obtain a kefir grain, aka a SCOBY (Symbiotic Colony of Bacteria and Yeast). You can mail order a kefir SCOBY, but there are usually people on Craigslist selling or giving them away.
• Add the SCOBY and milk to a large jar, typically about a tablespoon of grains per quart of milk, or 5% grains (Katz). Make sure that the jar has plenty of extra space to accommodate carbon dioxide produced. Cover the jar with a lid or cloth.
• Leave jar at ambient temperatures and stir or shake periodically. If your jar is sealed, release gasses as needed.
• The kefir will be ready to drink in 24 hours, or less if the air is hot. Leave the grain in longer if you prefer carbonation and a more acidic flavor. Strain or fish out the kefir grains and put them in fresh milk, and repeat the process.

Maintenance

• Kefir grains require regular use or they will die – if you'll be taking a long vacation, find someone to babysit. To suspend fermentation, cover with milk and place in the refrigerator, or freeze the grain. Your SCOBY will grow and reproduce over time; share the new grains with others.

Use

• Drink kefir plain or blend it with flavorings. Our standard recipe is 4 cups kefir, 1-2 cups frozen berries, ¼ cup sugar, and a splash of vanilla, put through a blender.
• Use kefir as a substitute for milk or buttermilk in recipes. Experiment and see what works.
• Strain kefir through a cheesecloth overnight to make a cheese or yogurt substitute. Mix with garlic, hot peppers, lemon, and fresh herbs for a dip or bagel spread.
• The fermentation process creates a product with barely any lactose, making this edible for who are slightly lactose-intolerant. Taste test before consuming large quantities if you're sensitive.
• Kefir grains are edible – chicken-fried SCOBY, anyone?

(Originally posted on the Laughing Duck Permaculture blog in 2014; from an unpublished dorm cooking zine I was working on in 2014; handed out in condensed form as leaflets at events and our farmer's market booth.)