In a Dutch oven, heat a little extra virgin olive and sauté the onion until lightly caramelized. Add the celery and cook for a few minutes.
In a frying pan, add a couple spoons of olive oil and when hot add the sausage and brown until caramelized. Constantly breaking the sausage up while it cooks so you have small uniform crumbles. When deep golden brown, remove the meat from the pan and drain any extra fat.
Back in the Dutch oven, add the mushrooms and sweat them for 5 minutes or however long it takes to eliminate the water. Add the thyme and garlic when fragrant, add fresh thyme, chopped tomatoes and tomato puree. Add the cooked meat, adjust with salt and pepper and let simmer slowly for 45 minutes.