In a large Dutch Oven heat the olive oil over medium-high heat. When the surface is rippling add the onions, green pepper and celery. Sauté until the onions start to soften and turn transluscent (5-10 minutes).
Add the ground beef and brown, using a spatula to break into small pieces while it cooks. Cook until no pink remains.
Add the chili powder, salt, pepper, dried oregano; stir to combine.
Pour in the tomato sauc, Italian parsley and mushrooms. Stir to combine.
Bring to a simmer. Simmer over low heat partially covered (to control splattering) for 2 hours. Stir the sauce every 30 minutes to ensure no sticking to the bottom of the pan.
When complete the sauce will have thickened and reduced to 8 cups yield.
Can be used immediately or within four days.
Notes
Due to the volume of vegetables it takes longer to begin to soften (10 minutes’ish).Simmer over the lowest setting to ensure it’s still cooking but to avoid sticking to the bottom of the pan.