Scrub and quarter potatoes, place in a large saucepan and cover with cold lightly salted water. Bring to a boil. Reduce heat and simmer for 8-10 minutes.

Add peas, cook 3-5 minutes longer or until vegetables are tender. Drain potatoes and peas, set aside.

In another large saucepan, melt butter and sauté onions until tender.

Whisk in flour, salt and pepper until blended, gradually add warm milk. Bring to a boil, stirring constantly. Cook and stir for 1-2 minutes or until thickened.

Toss in potatoes and peas, gently stir to coat. Serve immediately.