Creamy Spinach-Mushroom Stuffed Shells

Make it

Instructions

1. 01

   Prep the vegetables, pasta water, and baking dish

   Position one oven rack in the center and heat the oven to 375°F. Lightly coat a 9-by-13-inch baking dish with part of 2 tbsp olive oil; set it beside the stove. Wipe 8 oz cremini mushrooms clean with a damp paper towel, trim the stems, and finely chop them. Peel and finely dice 1 each yellow onion. Peel and mince 3 each garlic cloves. Rinse 5 oz baby spinach in a colander, spin or pat it very dry, and roughly chop it. In a large pot, bring 3 l water to a rolling boil over high heat; add 1 1/2 tsp kosher salt, reserving about 1/2 teaspoon for the filling. Add 24 each jumbo pasta shells and stir immediately. Boil until just pliable and 2 minutes shy of the package's al dente time, about 8 minutes. Drain thoroughly, then spread the shells in a single layer on a clean, lightly oiled baking sheet or plate so they do not stick; let them cool enough to handle. | Why: Undercooking the shells keeps them intact while they finish baking, and greasing the dish now prevents the saucy shells from sticking.

2. 02

   Cook the savory filling

   Heat the remaining oil in a large skillet over medium-high heat. Add the onion and mushrooms, then cook, stirring often, until the mushrooms have released their liquid and the pan looks nearly dry, 7 to 9 minutes. Add the garlic and cook until fragrant, 30 seconds. Add the spinach in handfuls, stirring until fully wilted, about 2 minutes. Scrape the mixture into a large bowl and cool for 5 minutes so it will not scramble the egg. | Why: Cooking off mushroom moisture concentrates its flavor and prevents a watery baked filling.

3. 03

   Mix the ricotta filling

   To the bowl of cooled vegetables, add 15 oz whole-milk ricotta cheese, 8 oz shredded low-moisture mozzarella cheese, 1 oz grated Parmesan cheese, 1 each large egg, 1/2 tsp black pepper, and 1/8 tsp ground nutmeg. Reserve about 2 ounces of the mozzarella for the top. Add the reserved salt, then stir until evenly combined and thick enough to mound on a spoon. | Why: The egg sets the cheese mixture while the three cheeses create a creamy filling with a browned, stretchy finish.

4. 04

   Fill and arrange the shells

   Pour 24 oz marinara sauce into the explicitly greased baking dish and spread it into an even layer. Spoon about 2 heaping tablespoons of filling into each cooled shell, then arrange the filled shells open-side up in the sauce. Sprinkle the reserved mozzarella evenly over the shells. Cover the dish tightly with foil, lightly tenting it so it does not touch the cheese. | Why: A layer of sauce protects the pasta from drying out, while filling before arranging keeps the shells neat and evenly portioned.

5. 05

   Bake, brown, and serve

   Place the covered dish on the center rack and bake until the sauce is bubbling around the edges and the filling is hot, 20 minutes. Carefully remove the foil and bake until the mozzarella is melted with browned spots, 10 to 12 minutes more. Rest the dish for 10 minutes so the filling firms slightly. Tear 1/4 cup fresh basil over the top, then serve 6 shells per portion with plenty of sauce. | Why: Covered baking heats the filling gently, and the uncovered finish browns the cheese without drying the pasta.