Clabbered milk is the most ancient way that people transformed fresh milk into a different food. How do I know that? Because the milk does it naturally. When raw milk is left to sit in a warm place, the friendly bacteria multiply and it becomes deliciously thick and tangy, almost like yogurt.
To make good clabbered milk, you absolutely MUST use raw milk. If you try this with pasteurized milk, it will just turn nasty and gross. Clabbered milk is loaded with a greater diversity of probiotics than yogurt. And because the lactose loving bacteria have converted most of the lactose into lactic acid, it's even easier to digest than raw milk (which is already much easier to digest than pasteurized milk). Clabbered milk is similar to yogurt, but much easier to make and even better for you.
And because it happens naturally, it's still easy for you to make today.
To get it going, all you have to do is take raw milk and leave it in a warm place (in the high 70's to low 80's F) where the bacteria can multiply. In the summer, on top of your fridge is a good place. During spring and fall if it's a little cool in your kitchen, make a warm water bath for the jar of milk in your sink. The water bath can start as warm as 100F because it will cool pretty quickly. In the winter, you can take advantage of whatever you use to heat your home, such as warmth from a wood stove or warm forced air. Just be careful that the milk doesn't get too warm. If you take the temperature of the milk once it has gotten as warm as you expect it to in that location, it shouldn't be any warmer than 90F.
Now, just be patient. Fresh milk will take two or three days to clabber. Use a glass jar so that you can watch its progress. You are looking for it to start separating ever so slightly into curds and whey. (Curds are milk solids, whey is the liquid.) When you put a finger or a spoon into it, it should feel thick and clotted, almost like yogurt. Once it has reached that point, if you leave it longer, the curds will continue to separate from the whey, leaving thicker curd and yellowish whey. Don't be alarmed if it separates--that is normal and natural. The ideal stage to catch it for most recipes is before it really starts to separate, but once it reaches complete separation, the curds can be strained into soft cheese and the whey can be used as starter for your next batch.
Once your milk has clabbered, it's very quick and easy to keep new batches going. Similar to a sourdough starter, all you have to do is add a portion of the clabber or whey to more fresh milk, let it sit in a warm place for 24 hours, and that milk will clabber. Sometimes if the milk wasn't quite warm enough, it won't be fully clabbered in that time, it might take longer. If you find that it's taking longer than you want, either find a warmer place for culturing the milk, or add more starter. It's ok to keep using the same jar without washing it, because the residual clabber in the jar provides the starter for your next batch.
You will learn what works in your house and how to fine tune your method.
I have been using the same half gallon jar for my clabber for years. I pour out the amount of clabbered milk that I need and refill it with fresh milk. The amount of previous clabber left in the jar might be as little as one cup, or as much as 4 cups. It definitely works faster if there is more pre-existing clabber compared to when there is less. Occasionally if milk solids build up inside of the rim, I scrape them down. Otherwise, I don't worry about how long it's been since the jar was washed, the quality of the clabber is excellent.
What do you do with clabbered milk?
Clabbered milk is so versatile! You can drink it by itself. It's slightly tangy, like unsweetened, not-as-thick yogurt. Or you can add berries and maple syrup to it and eat it for breakfast. Use it in place of yogurt in smoothies. Strain the curds from the whey in a tea towel to make soft cheese. Use the whey as the liquid in bread or feed it to animals or your garden. The whey also makes a good starter if you wish to make cultured butter.
I will create blog posts that highlight each of these uses, so stay tuned!