Step 1

Combine sugar and ½ cup hot water in a small bowl, stirring to dissolve sugar. Add ginger and let cool; drain and set aside.

Step 2

Bring chicken, stock, shallots, and garlic to a boil in a large saucepan. Reduce heat and simmer until chicken is cooked through, 20–25 minutes. Transfer chicken and garlic to a cutting board and let cool; discard shallots. Smash garlic to a paste using the side of a chef’s knife; return to saucepan and stir to combine. Shred chicken; set aside.

Step 3

Bring stock mixture to a boil and add rice. Reduce heat and simmer, stirring occasionally, until rice is tender and has broken (soup should have slightly thickened), 30–40 minutes. Stir in lime juice, fish sauce, and reserved chicken; taste and adjust seasonings with more fish sauce and salt if needed.

Step 4

Divide soup among bowls; top with reserved ginger, chiles, scallions, and peanuts.

Step 5

Do Ahead: Soup can be made 3 days ahead; cover and chill. Reheat over medium-low, adding water or stock to thin as needed.