Preheat the oven to 375. Remove the tops from the peppers and scoop out the seeds and ribs. Carefully trim the bottoms (if necessary) to ensure the peppers stand straight when upright. Place a steamer rack over a few inches of boiling water, or set a colander over a couple of inches boiling water in a large stock pot. Place the bell peppers in the steamer and cover. Steam for 10 minutes, and move to a baking dish or casserole.
Chop all of your vegetables (onions, yellow or orange bell pepper, kale, mushrooms etc) and the sausage. I remove the casing from the sausage; this is recommended. Remember, you are using all of this as your filling/stuffing for the bell peppers so you want everything chopped pretty small. When finished, heat olive oil in a pan or wok and stir-fry everything for about 5 minutes.
Heat 1 tablespoon butter in a saucepot with a tight-fitting lid over medium heat. Add the orzo and brown lightly, and then add the garlic and stir. After 30 seconds stir in the water or chicken broth. Bring to a boil, and then reduce heat to a simmer, cover and cook for about 15 minutes.
When the orzo is ready, mix with with your cooked veggies and sausage. Season with some of the parsley, and season with salt and pepper.
Stuff the peppers with the filling. Drizzle some olive oil over the peppers, pouring a little less than 1 tablespoon over top of each. Arrange the peppers in a casserole or small baking dish and roast for 40-50 minutes, until crispy at the edges and everything is cooked through.
Heat some tomato sauce about 2-3 minutes before the bell peppers are ready. Then, pour into your serving dish, or on top of your bell peppers; immediately after the bell peppers have come out of the oven. Place onto the dish and sprinkle with mozzarella or feta cheese and garnish with some parsley! Serve immediately while the peppers are still HOT! Enjoy!