Place 1 cup milk in a small crock or jar. Let stand at room temperature about 24 hours. Stir in 1 cup flour and let stand, uncovered, 2 to 4 days or until bubbles begin to form. Cover and keep refrigerated. This makes about 1 1/2 cups starter.

Each time you use a portion of starter, leave at least 1/2 cup remaining and replenish it by adding equal amounts of flour and milk. If you use 1 cup starter for a recipe, add about 1 cup flour and 1 cup milk. If you use 1/2 cup starter, add 1/2 cup each flour and milk. Let starter stand, covered, at room temperature 8 to 12 hours. Then return to refrigerator.

The starter needs to be replenished about every 10 days to keep the yeast alive and active. When not replenished at this frequency, the yeast may absorb all the sugar and perish from lack of food. If this happens, discard at least half the starter and add 1/2 to 1 cup milk and flour and let stand, covered, overnight. Refrigerate until ready to use.