Roasted Purple Yam Stew

Name: Roasted Purple Yam Stew
Ingredients: 4 ears corn; 1 lb shrimp, peeled and deveined, retaining shells; 4 cups water; 1 carrot, chopped; 1 teaspoon thyme; 2 small onions, chopped, divided; 2 lbs yams, purple; 4 tablespoons olive oil; 1 tablespoon Chinese five spice powder; 1 tablespoon kosher salt; 6 chili peppers, Calabrian, diced; 1 tablespoon fresh galangal root, grated; 1 ounce ginger, grated; 2 tablespoons garlic, grated; 5 ounces shiitake mushrooms, sliced (stems removed); 2 ounces green onions, sliced