To begin, combine plain flour and salt in a large mixing bowl. Gradually add water and knead for 8 to 10 minutes until a smooth and elastic dough forms. Cover with a damp cloth and rest for 30 minutes to soften the texture.
In a separate bowl, mix the minced chicken with onion, garlic, ginger, coriander, soy sauce, cumin, salt and pepper. Stir in the oil and combine thoroughly by hand until sticky. Cover and refrigerate for 20 minutes to let the flavours develop.
Divide the rested dough into small balls. Roll each into thin discs, about 3 inches wide. Place a spoonful of filling in the centre, then fold and pinch to seal into a half moon or round pleated shape. Keep the wrappers covered to prevent drying out as you fold.
Place the shaped momos into a lightly oiled steamer basket, ensuring they don’t touch. Steam over boiling water for 12 to 15 minutes, or until the dough becomes translucent and the filling is cooked through.
While the momos steam, char the tomatoes over a flame or under a grill until blistered. Toast sesame and cumin seeds in a dry pan until fragrant. Slightly roast the garlic and soaked chillies for a deeper flavour profile.
Add the roasted tomatoes, sesame, cumin, garlic, chillies, lemon juice and salt to a blender. Pour in mustard oil and blend into a smooth, pourable paste. Adjust salt and spice levels to taste.
Transfer the chutney to a saucepan. Stir in 2 cups of warm water or stock to loosen into a broth consistency. Simmer gently over low heat for 3 to 5 minutes until warm but not boiling.
Place 5 to 6 momos in individual bowls. Ladle over the warm jhol until the dumplings are partly submerged. The broth should coat but not drown them.
Garnish each bowl with fresh coriander, a drizzle of mustard oil and extra chilli if desired. Serve immediately while hot. Pair with sliced radish or crispy fried soybeans for added texture and contrast.