Cheesy Eggplant Rollatini
1 clove garlic, minced, or more to taste 1 cup grated Parmigiano-Reggiano cheese 1 cup shredded mozzarella cheese 1 pinch ground black pepper 1 teaspoon Italian seasoning, or to taste 1 ½ cups marinara sauce 2 eggplants, cut lengthwise into 1/4-inch sli… 4 cups fresh spinach kosher salt to taste ½ cup ricotta cheese ½ onion, chopped