Lay a trimmed cabbage leaf on your work surface. Position it so that the thicker side is pointing towards you.
Place a heaping tablespoon of filling near the center.
Fold the thick side of the cabbage leaf over the filling. Then, fold in the left and right sides. Roll the cabbage leaf away from you to seal in the filling.
Take one piece of softened scallion and use it to tie the cabbage roll like a parcel.
Repeat until all the cabbage leaves have been filled and tied.
Pour the bone broth into a pot. Add the lemongrass, garlic, ginger and chilies. Bring to the boil. Taste. Add fish sauce, as needed.
Drop the cabbage rolls one by one into the hot broth.
When the broth begins to simmer, set the heat to low, cover the pan and cook the cabbage rolls in the bone broth for 20 to 30 minutes.
Scoop out the cabbage rolls and place in soup bowls.
Strain the broth. Stir in the lime juice. Taste and add more fish sauce, if needed.
Pour hot broth over the cabbage rolls.
Garnish the Thai cabbage rolls soup with torn cilantro and lime wedges before serving.