Remove the skin from the chicken breast and slice into large, thin pieces. Marinate with 2 tablespoons soy sauce, 1 tablespoon sugar, 1 tablespoon paprika, 1 tablespoon oyster sauce, 1 tablespoon vegetable oil, 1 tablespoon five-spice powder, thinly sliced shallots, and thinly sliced garlic. Mix well to coat the chicken. After 30 minutes, add the chicken to a pan with sautéed shallots and cook, turning the pieces to brown both sides.

Adjust seasoning to taste. When the sauce has almost evaporated and the chicken is nicely colored, turn off the heat. Do not let the chicken get too dry.

Cut the chicken into small pieces and briefly marinate with a little fish sauce and sugar. Bring 1 large bowl (about 2 cups/480 ml) of water to a boil, add the chicken, and skim off any foam. Season the soup to taste, then add the napa cabbage and cook for a few more minutes. Turn off the heat and top with green onions, cilantro, and black pepper.