Ajiaco is the king of soups in Colombia, especially in Bogotá (where it is often called Santafereño). The key to its flavor is the mix of potatoes: papas criollas (small yellow potatoes that completely dissolve and thicken the soup), waxy potatoes (that keep their shape), and starchy potatoes (like Russet or Vivaldi).
The most important, yet often hard-to-find, ingredient is the herb Guascas. If you do not have it, you can substitute it with a small amount of oregano and/or cilantro, but the authentic flavor will be missing. Guascas is also sold dried in Latin markets.
In a large pot, combine the chicken broth, chicken breasts, tied scallions, garlic, salt, and pepper. Bring to a boil, then reduce heat and simmer for about 30 minutes until the chicken is cooked through.
Remove the chicken breasts and set aside. Remove the scallions and garlic from the broth. The broth is the soup base.
Add the papas criollas and Red Bliss/Yukon Gold potatoes to the broth, along with the Guascas herb (if using).
Bring to a boil and simmer for 20–30 minutes. The papas criollas must completely dissolve and thicken the soup into a creamy, heavy cream-like texture, while the other potatoes should remain in chunks. Stir occasionally to prevent the potatoes from sticking to the bottom. Mash some pieces if necessary.
Meanwhile, shred the cooked chicken breasts into medium-sized strips.
Once the soup reaches the desired thickness, add the pieces of corn on the cob and the shredded chicken.
Simmer for another 10 minutes until the corn is tender and the chicken is warmed through. Season with salt and pepper to taste.
Serve the Ajiaco hot, in deep bowls with 1–2 pieces of corn on the cob and shredded chicken.
The essential accompaniments: a bowl of heavy cream, a bowl of capers, and a plate of avocado slices – diners add these ingredients to their soup according to their taste. Sometimes, a small serving of white rice is also served.