Shepherds Pie

Name: Shepherd's Pie
Ingredients: 3 tablespoons olive oil, divided; 6 ounces slab bacon, cut into ½-inch pieces; 2 pounds ground lamb or beef; Kosher salt; 2 medium onions, finely chopped; 1 small fennel bulb, finely chopped; 1 large carrot, finely chopped; 2 celery stalks, finely chopped; 2 tablespoons tomato paste; 1 tablespoon all-purpose flour; 1 cup dry red wine; 2 cups low-sodium chicken broth; 1 tablespoon finely chopped rosemary; 1 tablespoon thyme leaves; 3 pounds Yukon Gold potatoes; 1 cup half-and-half or whole milk; ½ cup (1 stick) unsalted butter; 2 large egg yolks; ½ cup sour cream; Freshly ground black pepper; A potato ricer or food mill