Bring potatoes and salted water to a boil in a large saucepan and cook until tender. Drain potatoes and set aside. Cook bacon in a large skillet until crisp. Remove bacon and drain on paper towel and reserve two tablespoons of drippings in pan. Saute onions in pan and stir bacon and chives or dill. Layer in a lightly greased pan one thrid of potato slices, one third onion mixture, 2/3 cheese and sprinkle with 1/3 tea. salt and 1/4 tea. pepper. Repeat the layering procedure twice. Metl butter in pan and whisk in flour until smooth. Gradually whisk in milk until smooth. and pour over potato mixture and bake 400 degrees for 35 minutes until goldenbrown and bubbly.