Tortellini with milk

3 tablespoons butter , divided 1/2 cup chopped onion 4 cloves garlic , minced 1 (14 ounce) can tomato sauce 2 cups sliced fresh mushrooms 1/4 cup chopped[...]

2 medium potatoes 1 lb frozen mixed vegetables 1 lb cheese tortellini 1/4 cup margarine 1/4 cup all-purpose flour 2 cups milk 1/2 teaspoon salt pepper basil[...]