In a saucepan, cook the guanciale on med high heat in oil. Slowly caramelize and brown.  Add the English peas, favas, garlic and slowly saute. Add the sage and crushed red pepper. Saute for another 2 minutes.While cooking, boil salted water for pasta. Add tagliatelle to pasta water.
Add 2 cups pasta water to the guanciale mixture. 2 T of butter, 1 cup grated pecorino, salt and pepper. Drain pasta, and add to this mixture. Finish with more pecorino, EVOO and black pepper.