Preheat your oven to 375°F (190°C).

Boil a large pot of salted water. Add the pasta shells and cook according to package instructions until al dente. Drain and set aside to cool slightly.

In a large skillet, heat olive oil over medium heat. Add chopped mushrooms and cook until they soften, about 5-7 minutes.

Stir in minced garlic and cook for an additional minute, just until fragrant.

In a bowl, combine ricotta cheese, half of the mozzarella cheese, half of the Parmesan cheese, and the cooked mushroom mixture. Season with Italian herbs, salt, and pepper. Mix well until fully combined.

Take each pasta shell and fill it with the cheese and mushroom mixture.

Spread 1 cup of marinara sauce on the bottom of a 9×13-inch baking dish. Place the stuffed shells in a single layer, and pour the remaining marinara sauce over the top.

Sprinkle the rest of the mozzarella and Parmesan cheese over the stuffed shells.

Cover the dish with foil and bake for 25 minutes. Remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and golden.

Take the dish out of the oven and let it cool for a few minutes. Garnish with freshly chopped parsley before serving.