Yogurt Sour

Procedure

1. Warm the milk to about 98°F(37°C), or body temperature.
2. Stir in the yogurt.
3. Mix in the flour until smooth.
4. Pour into a sterile container, cover with a damp cloth, then cover tightly with plastic film.
5. Allow to stand in a warm place for 2–5 days, until bubbles form.