In a medium skillet, heat a drizzle of olive oil over medium heat. Add minced garlic to the pan, sautéing for about 1 minute until fragrant. Next, toss in the fresh spinach and cook until wilted, approximately 3-4 minutes. Once ready, remove from heat and let it cool slightly before finely chopping the mixture.

In a large mixing bowl, combine the ground beef or turkey with the egg, breadcrumbs, grated Parmesan cheese, Italian seasoning, salt, and pepper. Gently fold in the chopped spinach and garlic mixture using your hands to blend everything well. Take care not to overmix.

Scoop about two tablespoons of the meat mixture and flatten it slightly in your palm. Place a chilled mozzarella cube in the center and wrap the meat around it completely, sealing it tight. Repeat this process with the remaining mixture.

For baking, preheat your oven to 400°F (200°C) and arrange the meatballs on a lined baking sheet. Bake for 20-25 minutes until golden and cooked through. Alternatively, heat a skillet with oil over medium-high heat and pan-sear the meatballs for 6-8 minutes on each side until browned.

For a flavorful twist, after baking or searing, simmer the meatballs in warm marinara sauce for 5-10 minutes for added flavor.

Once cooked, remove the meatballs from the heat and let them rest for 5 minutes to allow the juices to redistribute.