Ham and Cheese Lasagna

Name: Ham and Cheese Lasagna
Prep time: 30 min
Cook time: 1 h 15 min
Total time: 1 h 45 min
Cuisine: European, Italian, Mediterranean
Ingredients: 4 tablespoons unsalted butter; 1/4 cup all-purpose flour; 4 cups whole milk; 1 tablespoon Dijon mustard; 1/2 cup freshly grated Parmigiano-Reggiano cheese; 1 pinch freshly grated nutmeg (about 1/4 teaspoon); kosher salt and freshly ground black pepper; 2 tablespoons extra-virgin olive oil; 1 tablespoon unsalted butter; 2 large (but not massive) leeks, trimmed, halved lengthwise, rinsed, and thinly sliced into halfmoons; 4 cloves garlic, minced; 5 sprigs fresh thyme, leaves stripped from the stem; 3 cups chopped ham (deli roasted ham is fine); 1 cup fresh whole-milk ricotta cheese; unsalted butter, at room temperature, for greasing; 8 ounces fresh mozzarella cheese, thinly sliced; 1/2 cup freshly grated pecorino cheese; 1 pound no-cook lasagna noodles; 5 ounces fontina cheese, grated