Step 1

Preheat the oven to 400˚. Bring a large pot of salted water to a boil. Add the pasta shells and cook 1 minute less than the package directs for al dente. Drain and spread out on a baking sheet.

Step 2

Heat the olive oil in a large skillet over medium high heat. Add the mushrooms and cook, stirring occasionally, until browned, 4 to 6 minutes. Reduce the heat to medium; stir in the thyme and half of the garlic and cook until the garlic is just golden, about 1 minute. Scrape into a large bowl and let cool for a few minutes.

Step 3

Add the ricotta, scallions, egg, 1 cup mozzarella and ½ cup parmesan to the mushrooms and stir to combine. Season with ½ teaspoon salt and a few grinds of pepper.

Step 4

Melt the butter in a large saucepan over medium heat. Add the remaining garlic; cook until sizzling, 30 seconds. Add the flour and stir to make a paste. Cook 1 minute, then stir in the wine. Bring to a simmer, then whisk in the half-and-half. Return to a simmer and stir in the spinach. Cook until wilted, 3 minutes. Stir in the lemon zest and season with 1 teaspoon salt and a few grinds of pepper.

Step 5

Spoon the mushroom filling into the shells.

Step 6

Spread one-third of the cream sauce in a 9-by-13 inch baking dish. Arrange the shells in the dish. Ladle the remaining sauce on top. Sprinkle with the remaining 1 cup mozzarella and ¼ cup parmesan. Bake until bubbly, 25 to 30 minutes. Let rest for 15 minutes. Serve with salad.