I’ve had some ups and downs making skyr, and no two batches have come out quite the same way.  The most reliable I’ve tried so far is based on the recipe in Complete Anachronist #143 “Skyr and Mysa: Viking curds and whey”.  The recipe is pretty easy, but very time consuming, particularly heating the milk without burning it.  I have yet to try this over the fire using Viking period equipment, but I’m hoping to do that sometime this summer. 

To make it at home, I use a gallon of skim (fat free) milk, and heat it up over a low flame in a very heavy pot until it hits around 185°, keeping it at that temperature for 10 minutes of so.  Then I turn off the stove, and let the milk cool down to just above body temperature, around 104°.  Then it’s cooled to that temperature, I add some starter culture.  I’ve used both Greek yogurt, and Siggi’s brand commercial skyr successfully.  Once that it well stirred, I add 8-10 drops of rennet mixed with a little water, and stir some more.  The trick from then on it to keep it as warm as possible for 6-8 hours.  The most successful batch I’ve made I left on the back of the stove while I cooked most of the day, so it stayed quite warm.  I’ve also tried insulating it with a blanket.  After 6-8 hours, it should be quite firmly set, and pulling away from the side of the pot.  It’s ready when it pulls away and when you can see clear whey floating on the surface.

Once it has set, spoon it into a sieve filled with cheese close or muslin and let most of the whey drain.  Then I hang it up in the cloth (tied into a bag) over a bowl overnight to drain.  In the morning you can take it out of the cloth.  It will be quite thick, and more or less sour depending on how warm it was kept while setting. 

It will keep for a while in the fridge, although it become progressively sour and eventually can turn quite bitter.  I’ve used it mixed into cooked vegetables, or with fruit or honey.

To make it over the fire, I would need to heat it up slowly enough without scorching it, which will take a lot of stirring.  I think the best way to keep it warm would be to pour it into a wooden bucket to set up.  The wood would keep it warmer, particularly if wrapped in wool.  I really need to find a wooden bucket I’m willing to sacrifice to dairy products.  Since the lactobacilli will stay in the wood, I don’t think I could use it for much else afterwards.