Preheat the oven to 400°F.
Wipe the mushrooms clean and remove the stems (don't discard the stems). Pick out the 12 best and largest caps, and set them aside.
Finely chop the remaining 4 mushroom caps and all of the stems (you can use your food processor for this). Set aside.
In a large pan, heat 2 tbsp of the oil over medium-high heat.
When the oil is hot, add the sausage and cook for 4 to 5 minutes, or until browned. Break the sausage apart with a wooden spoon as it cooks.
Add the green peppers, garlic, and chopped mushrooms and raise the heat to high and cook, stirring occasionally, for about 10 minutes, or until it is starting to brown and most of the liquid from the mushrooms has evaporated.
Reduce the heat to medium and stir in the bread crumbs and chicken stock (¾ cup). Cook for 2 minutes.
Turn off the heat and stir in the cheese and pickled cherry peppers.
Spread the mixture onto a platter and let cool for a bit.
Stuff each of the reserved mushrooms caps with 1½ tablespoons of the sausage mixture.
Place the stuffed mushrooms in a casserole dish and drizzle them with the remaining 2 tablespoons of oil. Add 2 tablespoons chicken stock into the dish.
Bake for 20 minutes.
Transfer mushrooms to a platter and spoon juices over the top.
Sprinkle with chopped parsley and a dusting of Romano cheese. Serve at once.