Place tomatoes in a large Dutch oven or stockpot, cover with water and boil for 25 minutes uncovered.
Drain and allow them to cool slightly, then process through a food mill or sieve to remove skins and seeds. Set aside.
In a large skillet, heat olive oil and sauté onions, garlic, and mushrooms until tender.
Place the sautéed vegetables in a large Dutch oven or stockpot, add tomatoes and remainder of ingredients and bring to a boil. Lower hea
Lower heat and simmer, uncovered, for approximately 25 minutes or until desired thickness, stirring frequently to avoid burning. Skim any foam from the top of the sauce as you stir.
Taste and add more brown sugar if desired as tomatoes vary in tartness. If more sugar is added bring to a simmer for 5 more minutes. Remove bay leaves.
Ladle into 1-quart jars leaving 1 inch of headspace. Cap and seal. Place in the pressure cooker with 4 to 5 inches of hot water.
Process at HIGH pressure for 25 minutes. Once done, allow pressure to come down naturally before opening the cooker.