Char the Poblano chilies over a gas flame until blackened on all sides.
Place them in a plastic bag and let stand for 10 minutes to steam.
Peel and core the Chilies.
Remove seeds, rinse and pat dry.
Cut Poblanos into thin strips, set aside.
Cut the porkloin in half lengthwise, cutting to-but not through-other side; open halves, laying the pork flat.
Cut each half lengthwise, cutting to-but not through-other side; open halves, laying pork flat.
Distribute the Poblano strips and cheese evenly over the pork; roll lengthwise and tie with kitchen twine.
Heat oil in a large dutch oven and brown pork roll on all sides; set aside.
Saute carrots, onion and celery in the dutch oven until softened, about 10 minutes.
Add bay leaves, salt and pepper to taste.
Place pork on top of the vegetables and cover with water.
Simmer until tender (there was not length of time given - I'm guessing at least 1 hour and maybe up to 2 hours - let me know what works when you try it please). (One review suggested 1 hour 15 minutes).
Add the tomato puree to the cooking liquid and continue cooking for 15 minutes.