In a glass jar add one litre of raw milk or pasteurized milk (not UHT milk), add approx. one TBSP of milk kefir grains. Cover the jar with a tea towel and secure it with a rubber. Leave it to ferment in the jar for 24 hours at room temperature. After 24 hours, drain the kefir grains and put the milk kefir in a clean jar (with no grains).
For a second fermentation, add flavor if desired, close it and leave it on the kitchen counter for 8-10 hours. The flavor will be slightly milder.
A second fermentation can be performed for the additional bacterial content, reduced lactose content, or simply for the improvement in flavor.
Fermenting the kefir a second time, no matter the additions, mellows the kefir and takes away some of the sharp acidic flavor milk kefir is known for. Because the kefir grains are removed before the second fermentation there is no risk of a contaminating or harming your kefir grains in any way.
Some flavoring ideas: Citrus fruit peels, vanilla + cinnamon, cocoa powder, chopped fruit. Just be aware that if you prefer not to have an effervescent kefir, wait until after the kefir has been fermented a second time before adding anything sweet.
Taking a break from kefir making
Put the milk kefir grains in a jar, add enough fresh milk and close the lid. Put it in the fridge. When you need to use them again, put them in the counter again with fresh milk and let them ferment for 24 hours or longer. You might need to try with a second batch as it might take some time for the kefir grains to wake again 🙂