1Heat oven to 350. Melt 3 TBLS butter in saucepan. Cook onion until translucent add flour and pepper stir till smooth.remove from heat add milk.bring to a boil and stir 1 min.
2Slice potatoes and put in 9x13 casserole dish. Pour mixture over top with 1 TBLS butter. Cover with foil bake for 50 min. Remove foil bake 1 hour