Place L. reuteri yogurt and a gallon of milk in a large pot and bring it to 80°F. Place a lid on it. Then turn off the heat and let sit for 24 hours or until you see a thick curd or a few billowy curds that form when you stir it.
After 24 hours or when you see a thick curd has formed, bring the pot to 100°F. Do it ever so slowly over low heat (about a degree every minute - 15-20 minutes), stirring every few minutes to break up the curds on the bottom of the pan so they won’t burn. You will know it’s done when the whey separates from the curd and you see soft fluffy curds floating. The whey is a clear yellowish liquid. If you are not seeing any whey you can take it to 102-103 F° and hold it for a minute or two until you see a little whey in the mixture and clouds of white.
Line a strainer with butter muslin (cheesecloth). Place the strainer over a bowl. Pour the mixture from the pot into the strainer a little at a time. I did this in two batches with the mixture, each time squeezing out the liquid (see next step) and removing the curds. Then I did it again till all the liquid was removed.
Drain the whey by twisting the bag and the whey will drain through the cheesecloth.
The finished curds may have consolidated somewhat but are easy to separate. You can now add a bit of salt to suit your preference (about ¼ - ½ teaspoon should do). This is not necessary if you want a salt-free product.
You can cover it with a little cream or milk and fresh fruit, nuts, granola, cinnamon, or whatever you liked. Options are endless.
Place in the refrigerator in a covered dish to store. This can last a few weeks and up to a month in the fridge. I love these vacuum seal containers from Luvele that make foods last 3-5 times longer and have a vacuum sealer. They're fabulous for food storage and especially for any cottage cheese.