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