01 - Preheat oven to 375°F.
02 - Boil the diced sweet potatoes in salted water until just tender, about 8 to 10 minutes. Drain and set aside.
03 - In a large skillet, heat olive oil over medium heat. Add the onion and garlic, sautéing until softened, about 3 minutes.
04 - Add the ground beef to the skillet and cook until browned, breaking it apart with a spoon, 5 to 7 minutes. Drain excess fat if needed.
05 - Stir in the drained diced tomatoes, dried oregano, paprika, salt, and pepper. Cook for an additional 2 to 3 minutes. Add the baby spinach and cook until wilted, if using.
06 - In a greased 9x13-inch baking dish, arrange half of the parboiled sweet potatoes in an even layer across the bottom.
07 - Spoon the ground beef mixture evenly over the sweet potato layer.
08 - Dollop the cottage cheese over the beef and spread it into an even layer.
09 - Arrange the remaining sweet potatoes on top, then sprinkle evenly with the shredded mozzarella and grated Parmesan cheeses.
10 - Bake uncovered for 25 to 30 minutes, until the cheese is bubbly and golden on top.
11 - Remove from the oven and allow the casserole to rest for 5 minutes before serving.