1 1/2teaspoonsfresh thyme leaves, plus some extra for garnish
15ounceswhole milk ricotta cheese
8ouncesshredded mozzarella cheese, divided
1/2cupshredded parmesan cheese
Preheat oven to 400 degrees.
Bring a large pot of salted water to a boil. Cook shells according to package directions for al dente.
Meanwhile, bring a small amount of water to a boil in a tea kettle. Place half of porcini mushrooms in a mug. Pour boiling water over them. Let sit for 10 minutes to reconstitute. Then drain and rinse under cold water. Chop into small pieces, then set aside. Put the other half of the porcini mushrooms in a food processor and grind into a powder.
In a skillet, melt butter over medium heat. Add cremini and shiitake mushrooms and season with salt and pepper. Cook, stirring occasionally, until the mushrooms have released their juices, about 5 minutes. Add garlic and thyme and cook for 1 more minute, stirring often. Remove from heat and set aside.
In a large bowl, mix together ricotta, 4 ounces shredded mozzarella cheese, parmesan, egg, chopped porcini mushrooms, porcini mushroom powder, and salt and pepper. Once the cooked mushrooms have cooled down a little, mix them in.
Spray a 9 inch by 13 inch baking dish with cooking spray. Make sure your shells have cooled enough to handle. Spoon about 1 tablespoon of the ricotta mixture into each shell. Place stuffed shells on baking sheet in a single layer. Sprinkle remaining mozzarella cheese over shells. Bake for 25 minutes. Garnish with fresh thyme just before serving.