4 med. potatoes (about 1 1/2 lbs.)
1/4 c. butter
1 sm. onion, chopped
1/2 c. Gruyere or Swiss cheese
1/2 tsp. salt
1/4 tsp. pepper
2 tbsp. water

Heat 1 inch salted water (1/2 teaspoon salt to 1 cup water) to boiling. Add potatoes. Heat to boiling; reduce heat. Cover and cook until tender, 30 to 35 minutes. Peel and shred potatoes or cut in 1/4 inch strips. Heat butter in 10 inch skillet until melted. Put vegetables in and sprinkle with salt and pepper. Cook, uncovered, over medium heat, turning often until potatoes start to brown, about 10 minutes (add 1 or 2 tablespoons butter to keep from sticking, if necessary).

Press potatoes with spatula to form a flat cake; sprinkle with water. Cover and cook over low heat, without stirring, until bottom is golden brown and crusty, about 10 minutes. Place inverted platter over skillet; invert on platter.