Soak beans in water 4 hours or overnight. Rinse beans and place in pot, cover with stock and water; add the halved onion and bay leaf. Bring to a boil, reduce heat a bit and simmer at a rapid bubble for 35-40 minutes until tender. Remove bay and onion, and purée half the beans and half their stock.
Heat a skillet over medium-high heat with EVOO, 4 turns of the pan. Add chopped pancetta and render 2-3 minutes then add the chopped onions, celery, carrots, rosemary, thyme, garlic, chili pepper and season with salt and pepper. Cook vegetables partially covered to soften, about 12-15 minutes, stirring occasionally.
Bring a pot of water to a boil for the pasta. When water is boiling, salt it, drop the pasta and cook to al dente.