Vegetarian Balsamic Mushroom and Spinach Stuffed Shells

Fill a large pot with lightly salted water and bring to a rolling boil. Stir in shells and return to a boil. Cook pasta uncovered, stirring occasionally, until tender yet firm to the bite, about 8 minutes. Drain carefully.

Heat butter and olive oil in a large skillet over medium-low heat. Add garlic; cook and stir until lightly browned, about 5 minutes. Add mushrooms and vinegar. Cook, stirring occasionally, until mushrooms are soft, about 5 minutes more. Drain any excess liquid and transfer mushrooms and garlic to a large mixing bowl to cool.

Rinse and dry skillet. Add olive oil over medium heat. Add garlic and cook until lightly browned, about 2 minutes. Add spinach and cook until wilted, 3 to 4 minutes. Add spinach to mushroom mixture in the mixing bowl.

Add ricotta, Italian cheese blend, Parmesan cheese, egg, basil, salt, and pepper to the spinach and mushroom mixture. Mix thoroughly to combine.

Preheat the oven to 375 degrees F (190 degrees C).

Open canned tomatoes and add basil, salt, oregano, and red pepper flakes directly to the can. Pour 1/4 of the sauce into a 9x13-inch baking pan.

Stuff each pasta shell with a large spoonful of filling and place, filling-side up, in the baking pan. Cover with remaining sauce and tightly cover with aluminum foil.

Bake in the preheated oven until heated through, about 30 minutes.

Sprinkle 2 tablespoons Parmesan cheese on top. Return pan to the oven, increase temperature to 400 degrees F (200 degrees C), and cook until bubbling, 15 to 20 minutes more.