Potatoes and Peas Au Gratin

2 pounds small new potatoes, cooked and peeled
1 bunch green onions, cut in 1-inch pieces
2 cups new peas, or 1 package frozen peas
2 cups thin cream sauce
1/4 cup grated American cheese

Cook onions and peas together until tender, about 10 to 15 minutes. Make cream sauce with 2 Tbsp. butter, 2 Tbsp. flour, 1 tsp. salt and 2 cups milk. Arrange potatoes and vegetables in buttered 1 1/2 quart baking dish. Add cream sauce and sprinkle grated cheese over the top. Brown in 350 degree oven for about 20 minutes.