Place chicken breasts in a large saucepan with 5 cups water, salt and peppercorns. Cook on medium heat for about 25–30 minutes, or until cooked through. Remove chicken breasts from broth and allow to cool. Shred and set aside. Reserve broth.

While chicken cooks, place cilantro in a blender, add about ¼ cup water and blend to make a thin mixture and set aside.

Heat oil in a stockpot over medium-low heat, add onion and red pepper and stir frequently until softened. Add garlic and cumin and stir for about 20 seconds until fragrant. Add aji and cilantro mixture; stir until combined. Season with salt and pepper to taste.

Add reserved broth to vegetable mixture. Add remaining 4¼ cups water, rice and potatoes; bring to a boil. Add chicken and chicken bouillon, stir and reduce heat to keep the soup at a simmer.

Add corn and peas, cover, and simmer until potatoes and rice are cooked through, about 15 minutes. Remove from heat to prevent rice from continuing to absorb the liquid. Add more salt, pepper or aji to taste and serve.

*Aji paste is available at Latin grocers.