Colombian Chicken and Potato Soup (Ajiaco)

Place the chicken breasts in a baking dish topped with the onion, garlic, salt, and pepper. Cover and refrigerate overnight.
Remove chicken from refrigerator and allow pieces to come to room temperature.
Heat the olive oil in a heavy bottomed lidded pot over medium-high heat.
Add the chicken along with marinade ingredients to the pot and brown the chicken on both sides.
Pour in the stock, add the guascas, bay leaves, green onions and salt and pepper. Bring to a boil, skimming foam, then reduce heat and simmer, covered, until chicken is cooked through, 10-15 minutes. Remove chicken and reserve broth.
Add frozen papas criollas (if using russet potatoes, peel and coarsely grate first) and more seasoning with the salt and pepper. Simmer until potatoes begging to break down about 30 minutes. Feel free to aid the process by using the backside of a wooden spoon to mash the potatoes against the sides of the pot until you get the consistency you desire.
Meanwhile, add the Yukon and New potatoes to the pot and simmer, covered, stirring occasionally, until almost tender, 10 to 15 minutes.
While potatoes simmer cut the chicken into shreds
Add the chicken back to the pot. Add cilantro, corn, the epis, salt and pepper and mix well. Then simmer 15-20 minutes
Serve topped with avocados, capers, and sour cream