Peel and cube the sweet potatoes and place into a large pot of water. Bring to a boil, then reduce heat slightly. Boil potatoes 15 to 20 minutes or until fork-tender. Drain and return to the pot. Add the coconut milk, ghee, salt and pepper. Mash well using a hand mixer. (Alternatively, you can process them in a food processor for a smoother texture).
Preheat the oven to 350 degrees.
To make the filling, heat a large oven-safe skillet over medium-high heat. Add the ground turkey and cook 8 to 10 minutes, breaking it apart with a wooden spoon. Season with salt and pepper. When the meat is no longer pink, push it out of the pan. Add olive oil, onions, carrots and celery. Continue cooking until vegetables are slightly tender, about 4 to 5 minutes.
Next, add the mushrooms, kale and garlic, cooking an additional 2 minutes. Add the tomato paste, curry powder, cumin, salt and pepper. Stir, cooking until the tomato paste is fragrant and well-incorporated, another 1 to 2 minutes.
Slowly add the broth to the pan, stirring frequently to incorporate well. If it needs thickening, dissolve arrowroot powder in a little extra broth and add to the pan. Stir and continue cooking until it thickens to your liking.
If your skillet is oven-safe, spread the sweet potato mash evenly over top the filling. If you do not have an oven-safe skillet, transfer the filling mixture to a 9 by 13 baking dish and spread the sweet potato mash evenly over top.
Bake the casserole for 30 minutes or until the filling is hot and bubbly. Cool 5 to 10 minutes, sprinkle with fresh chopped parsley, and serve.