Sourdough Starter - cooking recipe

Ingredients

1 pkg. active dry yeast
2 1/2 c. warm water
1 c. instant nonfat dry milk
2 Tbsp. sugar
4 c. flour

Preparation

Stir all but flour in a large nonmetal container until the yeast dissolves.
Stir in flour gradually until a smooth batter forms.
Let stand loosely covered in a warm place about 3 days, stirring down occasionally.
Refrigerate, loosely covered.