Step 1

Bring chicken, rice, garlic, ginger, and 5 cups water to a boil in a large saucepan. Add a big pinch of salt. Reduce heat to medium-low and simmer, uncovered and stirring occasionally, until rice has swelled and chicken is firm, 10–12 minutes. Add potatoes to pot and cook, stirring occasionally, until soup thickens, potatoes and rice are tender, and chicken is cooked through, 15–20 minutes.

Step 2

Transfer chicken to a cutting board and shred with 2 forks. Return meat to pot. Stir lemon juice and soy sauce into soup; taste and season with salt if needed.

Step 3

Ladle soup into bowls and top with cilantro and lots of pepper.

Step 4

Do Ahead: Soup (without cilantro) can be made 3 days ahead. Let cool; cover and chill. Reheat over medium-low, adding water to thin as needed.