Preheat the oven to 375°F (190°C).

Cook the pasta shells according to package instructions until al dente. Drain and set aside.

In a large skillet, heat some olive oil over medium heat. Add minced garlic and cook until fragrant.

Add ground beef to the skillet and cook until browned. Season with salt, pepper, and Italian herbs.

In a mixing bowl, combine ricotta cheese, shredded mozzarella, Parmesan cheese, chopped spinach, and a beaten egg.

Fill each cooked pasta shell with the cheese mixture and place them in a baking dish.

Pour marinara sauce over the stuffed shells and sprinkle with additional mozzarella and Parmesan cheese.

Bake in the preheated oven for 30 minutes, or until the cheese is melted and bubbly.

Let cool slightly before serving.