Heat the broth. Season with soy sauce and salt.
When the broth simmers, drop in the tofu and fried shallots, if using.
Simmer for about five minutes. Taste the broth and adjust the seasonings as the tofu is like a sponge that soaks up salt.
Drop in the pechay leaves, pushing them into the broth.
Turn off the heat, cover and leave for another five minutes to allow the pechay leaves to cook in the residual heat.