Green Peas with Onion and Mushrooms

1 pkg. (10 oz.) frozen peas, defrosted
1/2 onion, finely chopped
1/4 cup butter or margarine, 1/2 stick
1/4 lb. mushrooms, cleaned, sliced
4 slices bacon, cooked crisp, crumbled
1 tsp. chicken seasoned stock base
to taste: salt, pepper
3/4 cup sour cream 

    Defrost peas.  Sauté onion in butter until onion is transparent.  Add mushrooms and sauté until mushrooms are tender.  Add peas, bacon, stock base, salt and pepper; cover and cook until peas are almost tender.  Add sour cream and mix through.  If planning to serve at once, heat and serve; if not, place mixture in a heat-and-serve casserole; refrigerate.  Heat though just before serving.