Roasted Guinea Fowl with Chapelure de Legumes and Apple Cider Sauce

Name: Roasted Guinea Fowl with Chapelure de Legumes and Apple Cider Sauce
Ingredients: 2 small bulbs fennel; 2 small onions; 1 large celery root, peeled; 2 tart apples, such as Granny Smith, peeled and cored; 2 small carrots, peeled; 12 small red or fingerling potatoes, halved; 1 large bulb garlic, separated into unpeeled cloves; Kosher salt and freshly ground black pepper; 1/4 cup plus 1 tablespoon extra-virgin olive oil; 2 guinea fowl (2 pounds each); 1 bunch thyme or winter savory; 1 cup fresh apple cider; 2 tablespoons unsalted butter; 2 tablespoons Persillade