Colombian Chicken, Corn, and Potato Stew

INGREDIENTS

• 2 teaspoons dried oregano, crumbled
• 1 3/4 teaspoons salt
• 1 1/2 lb russet (baking) potatoes
• 1 cup water
• 2 lb yellow-fleshed potatoes such as Yukon Gold, peeled, cut into 1/2-inch cubes, and covered with water in a bowl
• 1 1/2 teaspoons black pepper
• 6 cups chicken broth
• 3 California avocados, quartered, pitted, peeled, and cut into 1/2-inch cubes
• 3 tablespoons drained capers
• 3 ears corn, cut crosswise into 1-inch pieces
• 1 (3 1/2- to 4-lb) chicken, cut into 8 serving pieces
• 1/2 cup chopped fresh cilantro leaves
• 3 tablespoons unsalted butter
• 1 large white onion, finely chopped
• 1 cup heavy cream