Sourdough Starter

1 package yeast
2 c. unbleached flour
2 tablespoons sugar (optional)

Dissolve yeast in 2 cups warm water in large bowl. Add flour and sugar; mix well. Let stand, covered, at room temperature for 48 hours or until bubbly and topped with pale yellow liquid. Refrigerate, loosely covered, until needed. Remove 1 cup starter every 7 to 10 days to use in recipe or discard. Then "feed" starter with 1 cup water and 1 cup flour, mix well. Let stand at room temperature for 1 hour or until bubbly. Refrigerate until next use.