This is 'strained yogurt', the same thing as authentic Greek yogurt; use it like cream cheese in recipes, or eat it with a little jam or fruit. Add a bit of salt if subbing this for cream cheese.
Since the whey- which contains the lactose, or milk sugar- is drained off, you end up with a product that has twice as much protein and quite a bit less milk sugar.
All you do is pour plain yogurt into a cheesecloth-lined colander, set it over a bowl overnight, and check on it in the morning. You can either leave it on the counter or do this in the fridge. The longer it drains, the thicker it gets. It works best with homemade, unthickened yogurt, since added thickeners make it hard for the whey to separate away from the solids. If you don't have cheesecloth, use something else that liquid can drain through but the solids won't, like the superstrong paper towels, or a clean flat-woven dish towel.
16 ounces of plain yogurt will yield about 8 ounces each of yogurt cheese and whey. You can substitute whey in place of buttermilk in recipes. I use it for part of the liquid when making bread.
1/2 c. (non-instant) powdered milk
1/2 c. water
1 c. sugar
2 Tbsp. butter, optional
To read more about making it or how to use it, see here.
If you happen to need it, here's a recipe for dairy-free sweetened condensed milk
Another great way to use sweetened condensed milk!