Wash potatoes, peel a thin strip around center, for attractive presentation ;-). Cook potatoes, covered, in boiling salted water for 15 minutes or until tender; drain.
Shell and wash peas (I use frozen). Cook peas according to package directions (basically cover and cook 8-12 minutes) until peas are tender. Drain.
Melt butter in a heavy saucepan over low heat; blend in flour, salt and pepper. Cook 1 minute, stirring constantly. Gradually add milk; cook over medium heat, stirring constantly, until thickened and bubbly. Combine vegetables and sauce.
To make in advance like for a covered dish dinner: place all in a casserole dish. Bake in a 350 degree oven for 30-45 minutes until bubbly. Yum!