Roughly chop the mushrooms, stems and all. Over high heat, heat the oil in a large, deep pot and sauté mushrooms until browned and reduced in volume. Add the onions and cook until they are very tender.

While the onions are cooking, in a blender combine the tomatoes, basil, parsley, garlic cloves and rosemary leaves. Blend until everything is complexly pureéd.

When the onions and mushrooms are softened and fragrant, add the tomato herb pureè to pot and cook for a few minutes. Add the tomato paste and water and stir until the tomato paste is dissolved.

Add the oregano, sugar, salt, black pepper and onion powder and stir to combine. Reduce heat to very low and add the bay leaves; let simmer for 30 minutes.

Remove pot from heat, remove the bay leaves and allow to cool slightly. Blend the mixture until just slightly chunky.

Use in your favorite recipes immediately or store in the refrigerator over night to allow flavours to bloom. Use the next day.