Preheat the oven to 350 degrees F.
In a small or medium saucepan with a lid, bring 1 1/2 cups stock to a boil. Add a pinch of salt if you've used low-sodium or unsalted stock. Add a pinch of black pepper. Add the rice and stir. Place the lid on the saucepan. Lower the heat to low/gentle simmer and cook for 15 minutes, or until the rice is cooked and the liquid is absorbed. Remove the pan from the heat and allow it to sit for 5 minutes. Scrape the rice into a large mixing bowl and set aside.
While the rice is cooking, cut the peppers in half from the top to the bottom. Remove any membranes, seeds, and the thick, white part of the core and discard.
Place the peppers in a bowl with about an inch of water, layering them on top of each other is fine. Microwave them for about 8 minutes on high, or until just softened. (If your microwave is large enough to hold your 9x13” dish, you can place the peppers cut-side up in the dish with about a cup of water and microwave them to soften. Pour out the water before filling; you may have to remove the peppers to drain, then return them to the dish.) If you microwaved the peppers in a bowl, once softened, place them cut-side up in the baking dish. Set aside.
Brown the ground turkey in a medium skillet (nonstick works well) until cooked completely through. Drain and set aside while you prepare the remaining ingredients.
In the same skillet, heat 1 tablespoon of oil over medium-high heat. Add the sweet potato and leeks. Cook, stirring often, until the sweet potato is just tender, approximately 5 to 7 minutes. Some caramelization is fine and good.
Add the shallot and stir often until just softening, about 2 minutes. Add the garlic and stir for about 20 seconds. Turn the heat off and add the Worcestershire sauce, all-purpose seasoning, and 1/4 to 1/2 cup of the stock to moisten the mixture. You should have cooked the ground turkey completely, so the mixture should be safe to taste for seasoning. Adjust seasonings as needed.
Scoop and mound the mixture evenly into the 8 pepper halves. Top with the cheese.
Bake in the oven for 30 minutes, or until the filling is bubbling and the cheese is melted.
Remove from the oven and sprinkle with the green onions and parsley.
Serve very warm.