Wild Mushroom Lasagne

Name: Wild Mushroom Lasagne
Ingredients: 3 cups water; 2 ounces dried porcini mushrooms (about 1 cup); 2 pounds fresh white mushrooms; 2 large zucchini (about 1 pound); 1 large onion; 3 garlic cloves; 5 tablespoons unsalted butter; 6 tablespoons Sherry; 2 teaspoons chopped fresh thyme leaves; 2 1/2 teaspoons salt; 1/4 teaspoon freshly ground black pepper; 1 stick (1/2 cup) unsalted butter; 1/2 cup all-purpose flour; 5 cups whole milk; 4 1/2 ounces freshly grated Parmesan (about 1 1/2 cups); 2 teaspoons Dijon mustard; 1 1/2 teaspoons salt; eighteen 7- by 3 1/2-inch sheets dry no-boil lasagne (about 1 pound); 1/2 pound freshly grated mozzarella (about 2 cups); 1 1/2 ounces freshly grated Parmesan (about 1/2 cup)