Lasagne with Wild Mushrooms, Leeks and Gorgonzola

Ingredients

• 1 pound dried lasagne noodles
• 15 ounces ricotta cheese
• 3/4 cup grated Parmigiano-Reggiano cheese
• Salt and freshly ground black pepper
• 1/4 cup extra-virgin olive oil
• 5 large leeks, white plus 3 inches of the green part, cut into 1-inch dice
• 1 1/2 pounds wild mushrooms, thinly sliced
• 5 garlic cloves, minced
• 1/4 cup (1/2 stick) unsalted butter
• 4 1/2 tablespoons all-purpose flour
• 3 1/2 cups whole milk
• 6 ounces Gorgonzola, Stilton, or Roquefort cheese
• Freshly grated nutmeg
• 4 ounces whole-milk mozzarella cheese, coarsely grated