In large stock pot, heat oil over medium/medium-low. Add onion and garlic and sauté until it starts to brown, stirring often. Approximately 2-3 minutes.
Add mushrooms to pot, stir, and cook until they have released most of their liquid. 5-7 minutes.
Add whole tomatoes (with fluid) and fresh diced tomatoes and bring heat up to medium. Stir well, break up whole tomatoes a bit with a wooden spoon as you stir.
Add oregano, rosemary, basil, salt, and pepper and mix well.
Turn heat down a little to medium-low, and let rapid simmer for at least 45 minutes, stirring often. Or low and let it gently simmer, although it will reduce more slowly at a lower temp.
Once it has thickened to your liking, serve over your favorite pasta or lasagna.
Notes
Substitute crushed tomatoes for whole, or substitute another can of 28 oz tomatoes for the fresh romas. Our favorite brands are Muir Glen or Cento San Marzano.Substitute dried herbs for fresh by subbing 1 teaspoon of dried herbs for every 1 tablespoon of fresh herbs.To freeze: Let cool completely and then add to freezer safe bags / containers for up to 3-4 months.Store in airtight container and store in fridge for up to 5 days.