This is the kind of dinner that tastes hearty and comforting without feeling heavy. The mushrooms stand in for the ground meat filling often found in some stuffed shell recipes, and with sautéed spinach, they offer a satisfying portion of vegetables. Since cooking times for the pasta shells can vary based on the brand you use, keep an eye on the shells as they cook, and pull them out when just al dente. This way they won’t be overcooked once filled and baked. You can usually find mixed packs of pre-cut mushrooms in the vegetable section, near the herbs, but if you can’t find them, just substitute an equal quantity of whole mushrooms.
How to Make It
Preheat oven to 400°F. Cook shells in boiling salted water according to package directions for al dente pasta. Drain.
Heat 1 tablespoon oil in a large skillet over medium. Add onion and garlic; cook, stirring often, until softened, about 5 minutes. Stir in tomatoes, 1½ teaspoons salt, and ¼ teaspoon pepper. Cook, stirring often, until slightly thickened, 6 to 8 minutes. Reserve ½ cup sauce. Spoon remaining sauce into a lightly oiled 13-by-9-inch baking dish.
Wipe skillet clean and heat 1 tablespoon oil over medium-high. Add mushrooms and remaining ¼ teaspoon salt and ½ teaspoon pepper; cook, stirring occasionally, until browned, about 5 minutes. Transfer to a bowl. Add remaining 1 tablespoon oil to skillet. Add spinach and cook, tossing, until wilted, about 1 minute.
Stuff shells with ricotta, mushrooms, and spinach and arrange in baking dish. Top with reserved cup ½ sauce and Parmesan. Bake until shells are heated through and cheese is melted, 12 to 15 minutes.