Wash hands with soap and water.

Prepare a large casserole baking pan by coating lightly with oil or cooking oil spray.

Place a layer of potatoes in pan, using approximately 1/4 of potatoes.

Sprinkle layer with 1/4 cup chopped raw onion, 1/2 tablespoon margarine, 1 tablespoon flour, 1/4 teaspoon salt, and sprinkling of black pepper.

Repeat layers, making a total of 4.

Meanwhile heat milk over low heat.

Pour warm milk over all ingredients in casserole dish.

Bake at 350 °F for 1 hour.

Refrigerate leftovers within 2 hours.

Wash hands with soap and water.

Prepare a large casserole baking pan by coating lightly with oil or cooking oil spray.

Make a white sauce by melting margarine in a small pan. Stir in flour. Gradually add milk, stirring constantly.

Cook, stirring constantly, until slightly thickened. Remove from heat.

Add salt and pepper.

Place a layer of potatoes and onion in a prepared casserole pan, using approximately 1/4 of the potatoes and 1/4 cup onion.

Spread with 1/2 cup of the sauce prepared in steps 2 and 3.

Repeat layers, making a total of 4.

Bake at 350 °F for 1 hour.