01 - Preheat the oven to 400°F. Lightly grease a 9x13-inch baking dish.
02 - In a large skillet over medium heat, add olive oil. Sauté onion and red bell pepper for 3-4 minutes until softened. Add garlic and cook for 1 minute until fragrant.
03 - Add ground turkey, breaking it up with a spoon, and cook until browned, about 5-6 minutes.
04 - Stir in smoked paprika, thyme, cumin, chili powder, salt, black pepper, and red pepper flakes. Mix well.
05 - Add chopped spinach and cook for 1-2 minutes until wilted. Remove from heat.
06 - In a large bowl, toss sweet potato cubes with a pinch of salt and pepper. Add them to the prepared baking dish.
07 - Spoon the turkey and vegetable mixture evenly over the sweet potatoes. Drizzle milk over the casserole, then sprinkle the shredded cheddar cheese evenly on top.
08 - Cover with foil and bake for 25 minutes.
09 - Remove foil and bake for another 15 minutes until sweet potatoes are tender and cheese is golden and bubbly.
10 - Let rest for 5 minutes. Garnish with fresh parsley if desired. Serve warm.