Pastitsio

Name: Pastitsio
Ingredients: 1/4 cup extra-virgin olive oil; 1 medium yellow onion, chopped; 1 teaspoon red pepper flakes; 2 cloves garlic, minced; 2 teaspoons herbes de Provence; 1 1/2 teaspoons plus 2 pinches four-spice powder (quatre epices); 2 pounds ground lamb shoulder; 1/2 cup white wine; One 28-ounce can tomatoes, pureed; Kosher salt and freshly ground black pepper; 2 1/2 cups milk; 4 tablespoons butter; 1/4 cup plus 1 tablespoon all-purpose flour; 3 egg yolks, at room temperature; 2 cups grated Pecorino Romano; 1 cup full-fat Greek yogurt; 1 pound ziti pasta; 1 cup fresh parsley leaves, minced