Cook potatoes on layer of paper towel in oven, first pricking skin of each at least once with a fork to prevent bursting during cooking.
Cook 8 to 9 minutes or until potatoes begin to soften when pressed.
Remove and set aside.
Shell peas and wash.
Place in serving dish, add 2 tablespoons water and cook covered with plate or plastic wrap, 5 minutes.
In 4-cup measure, combine butter and onion.
Cook uncovered, 1 minute, stirring once.
Blend in flour, salt, dill and pepper.
Stir in milk, mixing well.
Cook uncovered, 3 minutes, 30 seconds or until mixture boils.
Meanwhile peel potatoes and arrange in serving dish with peas.
Pour sauce over vegetables.
If necessary, reheat by cooking uncovered, 1 to 2 minutes or until hot.