Ajiaco (Colombian Chicken Soup)

For the soup:

• 3 lb. cut-up chicken, skin removed, rinsed well
• 1 large white onion, peeled and cut into quarters
• 1 leek (white and light green parts only), cut into 1-inch rings, and rinsed thoroughly
• 1 green bell pepper, seeded and cut into 1-inch pieces
• 2 ears fresh corn, cut crosswise into quarters
• 2 ribs celery, cut into 1-inch pieces
• 2 large carrots, peeled and cut into 1-inch pieces
• 3/4 lb. Yukon Gold potatoes, peeled and cut into 1-inch cubes
• 3/4 lb. Idaho potatoes, peeled and cut into 1-inch cubes
• 3/4 lb. small red potatoes, peeled and cut into 1-inch cubes
• 6 cloves garlic, peeled
• 1/2 cup fresh cilantro leaves
• 2 chicken bouillon cubes
• 1 Tbs. kosher salt; more to taste
• 1/2 tsp. ground black pepper

For the aji:

• 4 scallions (white and light green parts only)
• 1 medium tomato, peeled and seeded
• 1 small white onion, peeled
• 2 fresh Scotch bonnet or habanero chiles or 2 fresh hot red chiles, stems and seeds removed (wear gloves, and don’t touch your eyes)
• 3 Tbs. fresh cilantro leaves
• 3 Tbs. white vinegar
• 1/4 tsp. kosher salt

For the garnishes:

• 2 ripe avocados, peeled and cut into 1/2-inch cubes
• 1 cup sour cream or crème fraîche
• 1/2 cup nonpareil or other small capers, rinsed and drained (if using large capers, chop them coarsely)
• 1/2 cup chopped fresh cilantro leaves