Country Gardens Pasta Sauce

2 cups chopped onions
1/2 to 3/4 cup butter
2 green peppers, seeded and chopped
3 large celery stalks, chopped
2 cloves garlic, minced
1/2 pound fresh mushrooms, sliced
2 medium zucchini, chopped
12 large fresh tomatoes, peeled and chopped, or
    2 (28 ounce) cans whole tomatoes, chopped and not drained
1 (12 ounce) can tomato paste
1 tablespoon chopped fresh basil or 1 teaspoon dried basil
1/2 teaspoon thyme
1 tablespoon chopped fresh oregano or 1 teaspoon dried oregano
1 bay leaf
2 teaspoons salt, or to taste
Freshly-ground pepper, to taste

Sauté onions in 4 tablespoons of the butter for 2 minutes. Add peppers, celery and garlic; cook until onions are translucent. Place in a 4- to 6-quart heavy skillet. Add 2 tablespoons of butter to the skillet and add the mushrooms. Sauté over medium high heat for 2 to 3 minutes until they have absorbed the butter. Add to the onion mixture. Put the remaining butter into the skillet and add the zucchini. Brown for several minutes and add to the onion mixture. Add the tomatoes, tomato paste, herbs, salt and pepper. Simmer for 45 minutes to 1 hour.