Coq au Vin with Cocoa Powder

Name: Coq au Vin with Cocoa Powder
Ingredients: 1 3½–4-pound chicken, cut into 8 pieces (legs and thighs separated, breasts halved); Kosher salt, freshly ground pepper; 1 large yellow onion, chopped; 1 large carrot, peeled, chopped; 1 bunch thyme; 2 bay leaves; 1 750 ml bottle red wine, preferably Côte du Rhône; 3 tablespoons olive oil, divided; 2 tablespoons unsalted butter, divided; 5 ounces thick-cut bacon, cut into ¼-inch pieces; 8 ounces button mushrooms, halved; 1 tablespoon all-purpose flour; 8 ounces pearl onions, peeled; 1 tablespoon red wine vinegar; 1 tablespoon unsweetened cocoa powder