Heat the oven to 400°F/205°C. Coat a small 3-cup casserole dish or ovenproof skillet with nonstick spray.

Warm 1/2 tablespoon olive oil in a nonstick skillet over medium-high heat. Cook the onions for 5 minutes until softened, then add the turkey, chili powder, and onion powder. Cook until the turkey is fully browned and crumbled, then transfer to a bowl.

Add the remaining 1 tablespoon olive oil to the skillet and lower the heat to medium-low. Cook the garlic and sage for 2-3 minutes, then add the spinach and stir until wilted, about 2 minutes. Transfer the spinach mixture to a bowl.

Whisk the eggs and milk together in a mixing bowl. Add the cooked turkey, spinach, potatoes, and Mozzarella cheese, then stir until evenly combined.

Move the mixture into the prepared casserole dish and sprinkle the Parmesan cheese over the top.

Bake for 20-25 minutes until the top is golden brown and the casserole springs back when touched. Season with salt and pepper to taste.