1. Use a spoon to scrape ribs from underside of Portobello caps and discard along with stem. Then cut into bite sized pieces.
2. In a very large skillet or sauté pan, heat oil over medium heat and add pancetta.
3. Cook for ten minutes or until crisp.
4. Add shallots and cook for three minutes.
5. Add garlic and rosemary and cook for one minute.
6. Add tomato paste and cook for two minutes.
7. Add butter and all mushrooms and stir. Increase heat to medium high, cover and cook for five minutes.
8. Remove cover and cook for five more minutes.
9. Add stock, salt and pepper and cook uncovered over medium low heat for 15 minutes or until most of the liquid is gone and the mushrooms are tender.
10. While mushrooms are cooking, prepare fettucine according to package directions.
11. Drain pasta but save a cup of the pasta water.
12. Add parsley and Romano to the mushrooms and add a little of the pasta water to make a creamy thick mixture. Add only enough water to get the right creamy constancy. We used about half a cup.
13. Serve over cooked fettucine. Serve with additional parsley and Romano cheese, if desired.