About 2/3 of a 12-ounce box jumbo shells (see note 1)
small yellow onion, finely diced
garlic cloves, minced
ounces sliced shiitake mushrooms
ounces baby spinach
pound fresh ricotta cheese
cup grated pecorino romano, divided
teaspoon fine sea salt
Freshly ground black pepper
ounces fresh mozzarella, sliced
cups good tomato sauce
cup minced fresh flat-leaf parsley to garnish, optional
Preheat oven to 375°F.
Boil pasta shells in well salted water according to package instructions. Drain and toss with a teaspoon of the olive oil to prevent sticking.
Meanwhile, warm the tablespoon of olive oil over medium-high heat in a 12-inch nonstick skillet. Add the onion, garlic and shiitakes along with a big pinch of salt and cook, stirring occasionally, until softened, 5-10 minutes. Add spinach and cook until wilted. Place spinach mixture into a large bowl and stir in ricotta, half the pecorino, the salt and a few good grinds of pepper. Crack the egg into the bowl, beat well with a fork and then stir into mixture.
In a standard 9x13-inch baking dish, spread 1/2 cup or so of the tomato sauce. Fill each pasta shell with a couple of tablespoons of the vegetable-cheese mixture and place in a single, snug layer into the baking dish, continuing until all shells and filling are used. Pour remaining tomato sauce over shells and top with mozzarella and remaining pecorino. Bake for about half an hour, until hot and bubbly. Sprinkle with parsley and serve.
I used Ronzoni jumbo shells because that's what our local grocery store had available. There are 42 per 12-ounce box, and 35 fit snugly into my 9x13-inch pan. It looks like Barilla jumbo shells are bigger, with 35 per 12-ounce box. Whatever brand you use, make enough shells to fit snugly into the baking pan, and use up all the filling -- the shells are pretty flexible.
I've been enjoying the blog Garlic & Zest recently, where my friend Lisa posted a recipe for Mushroom and Kale Stuffed Shells. Pretty sure that's where I got the idea to add mushrooms to this dish, not that I really ever leave mushrooms out of anything. Check out her site. You'll like it.
So here's something from 2018: we discovered that if you're not feeling vegetarian at the moment, a pound of hot Italian sausage makes a tasty substitution for shiitakes. As your first step, cook the sausage on medium-high in the skillet until browned and cooked through, then place it in a big mixing bowl. Pour off all but two tablespoons of the fat from the pan and sauté the onion and garlic in that instead of olive oil, then proceed with the recipe as written, omitting the shiitakes. Juuuuust sayin. :)