Pioneer Scalloped Potatoes

4 cups peeled and thinly sliced potatoes
1 teaspoon salt
1/8 teaspoon pepper
2 tablespoons flour
2 tablespoons onion, finely sliced or grated
2 tablespoons butter or margarine
1/8 teaspoon baking soda*
2 cups milk (about)

In a 2-quart baking dish -- layer potatoes, salt and pepper, flour, onion, and bits of butter. Add baking soda to milk, then pour it over the potatoes. Use enough milk so that it can just be seen between the top slices of potato. Cover and bake at 350 degrees F. for about 20 minutes. Remove cover and continue to bake about another 40 minutes, or until potatoes are fork tender and milk is mostly absorbed. Top will brown slightly. 6 servings

*Soda may be eliminated, but it keeps the cooked mixture from looking curdled.