Regrease your pot with the remaining ghee and add your onion and garlic, cooking 3 minutes, or until fragrant. Add your bell peppers and cook 3 more minutes, before adding the tomatoes, mushrooms, red pepper flakes, oregano, parsley (reserving some for garnish), bringing to a boil and cook an additional 3-5 minutes. Add your sausages back to the pot, placing it under the broiler for 5-10 minutes, so the sausage is well browned and the sauce is bubbling. Set aside to cool before serving.