In a skillet, heat a teaspoon of olive oil over medium heat. Add 2 cups of fresh spinach and 2 minced garlic cloves, sautéing for about 3-4 minutes until the spinach wilts and the garlic becomes fragrant. Remove from heat and allow to cool slightly before finely chopping the mixture to incorporate it into the meatball blend.

In a large mixing bowl, combine 1 pound of ground beef or turkey with the chopped spinach and garlic mixture, 1 beaten egg, 1 cup of breadcrumbs, ½ cup of grated Parmesan cheese, 1 tablespoon of Italian seasoning, and salt and pepper to taste. Mix gently with your hands until just combined, being careful not to overmix.

Using your hands, scoop a portion of the meat mixture and flatten it slightly in your palm. Place a chilled mozzarella cube in the center and encase it completely by rolling the mixture into a ball. Seal any gaps.

Preheat the oven to 400°F (200°C). Place the formed meatballs on a parchment-lined baking sheet and bake for 20-25 minutes until golden brown and cooked through.

For added moisture and flavor, optionally simmer the cooked meatballs in warm marinara sauce for 5-10 minutes.

Once cooked, remove from the oven or sauce and let rest for about 5 minutes before serving.