If you don’t have leftover squash or sweet potatoes on hand, preheat the oven to 375 degrees. Line a large baking sheet with parchment paper or aluminum foil.
Place the squash on the prepared baking sheet. Drizzle with 1 tablespoon of olive oil, season with salt, pepper, and a pinch of cinnamon, and toss to coat. Arrange the squash in an even layer and roast for 25 to 30 minutes, stirring once halfway through the cooking time, or until just tender.
Meanwhile, combine the quinoa and chicken broth in a small saucepan. Bring to a boil, then lower to a simmer. Cover the saucepan with a lid and cook for 15 minutes or until all the liquid has been absorbed. Let stand for 5 minutes, then fluff with a fork.
Transfer the quinoa to a large mixing bowl and add the roasted squash, turkey, greens, cranberry sauce, gravy, thyme, and half of the Fontina cheese. Fold everything together until combined. Taste and season with salt and pepper if needed.
Transfer the quinoa filling to a medium casserole dish or large ovenproof skillet and lightly smooth the top with a spatula. Sprinkle with the remaining Fontina. Briefly set aside.
Heat the remaining tablespoon of olive oil in a small skillet over medium heat. When the oil is hot and shimmering, add the garlic and cook for about 30 seconds to a minute or until golden (be very careful not to burn it!!). Stir in the panko and cook until lightly browned, about 2 minutes. Sprinkle the toasted breadcrumbs over the casserole.
Bake the casserole for 25 minutes until the cheese has melted. Serve warm with extra gravy and cranberry sauce.