Step 1

Place the chicken breasts in a large (at least 8-quart) pot. Add the russet and Yukon Gold potatoes, scallions, corn cobs (without kernels), celery, cilantro, garlic, 2 teaspoons salt and 1 teaspoon pepper. Add 6 cups water and bring to a simmer over high, occasionally skimming off and discarding the foam that rises to the top. Reduce to medium and simmer, uncovered, until the thickest part of the chicken breasts reach 160°F, 25 to 30 minutes.

Step 2

When the chicken is done, use tongs to transfer it to a plate; set aside. Remove and discard the corn cobs, celery, scallions and cilantro from the broth. Stir in the cut pieces of corn on the cob and the waxy potatoes. Return to a simmer over medium-high, then reduce to medium and simmer, uncovered and stirring occasionally, for 5 minutes. Transfer the corn on the cob to a bowl. Continue cooking the soup, stirring occasionally, until the waxy potatoes are tender and some of the other potatoes have begun to break down, another 20 to 25 minutes.

Step 3

Meanwhile, shred the chicken breasts into bite-size pieces, discarding the bones. Transfer to a bowl, cover and set aside until ready to serve.

Step 4

Add the corn kernels and guascas (if using) to the pot. Cook, stirring often and scraping along the bottom of the pot to prevent scorching, until the corn is tender-crisp, about 5 minutes. If desired, thin the soup with a little hot water. Taste and season with salt and pepper, then remove from the heat.

Step 5

To serve, place the capers and avocados in separate bowls; put the cream into a small pitcher. Ladle the soup into individual bowls. Serve with the corn on the cob, chicken, capers, avocados and cream, allowing diners to garnish their bowls as desired.