For just over $3.00 for a gallon of milk and a container of yogurt, you get 16 cups with this recipe so it is definitely more cost effective if there are yogurt eaters in the family. Along with preserves as a flavoring agent, you can use canned fruit, pureed or not, with or without the syrup, or thawed frozen fruit, fresh fruit, even some of the canned pie filling.
1 gallon milk
1 cup real yogurt (must contain live cultures for use as
a starter), either homemade or store-bought.
In large pot, boil milk until the froth rises almost to the top of the pot, then remove from heat. Let it cool until it is almost body temperature. (You'll know it's ready when you can close your eyes, put your finger in the milk and you can't tell that it is in the milk because there's no dramatic difference in temperature between room and milk.)
Once cooled, add 1 cup yogurt to the milk. Mix well, then cover pot and wrap it in a blanket or heavy towel. Put it in the corner of the room (or somewhere it will stay warm and out of the way) for about 6 hours. (If you want a more tart flavor, leave it wrapped for 8 or 9 hours. For a sweeter, softer style, leave it out only about 4 hours.) Then refrigerate for 10 hours.
Always keep 1 cup of your previous batch for use as a starter for a new batch. Makes 16 cups.
NOTE: For low-fat yogurt, start with low-fat milk.