Peel the onion and chop into 2-inch chunks.
Add the chopped onion to a pot along with the chicken broth and the water. Boil without a lid until almost all liquid has evaporated.
Puree the onion in a food processor. Set aside.
Heat the oil in a Dutch oven or a cast iron pan to which you have a lid.
Add mustard, cumin and coriander seeds to the oil and fry on medium-low heat for 2 – 3 minutes. (The seeds need to sizzle but be careful not to burn them.)
Carefully add the onion puree. (Be careful, this might splatter; keep a splatter screen ready).
Fry the onion puree for 7 minutes on medium heat.
Add ginger, turmeric, garlic and curry and stir until well combined.
Add the chicken pieces and fry for about 2 minutes.
Add tomato paste, coconut milk and soy sauce and mix well.
Add bell pepper and pineapple, bring to a boil, cover loosely with a lid and simmer for 10 minutes.
Season to taste with a little bit of salt, then sprinkle with lime juice to taste. Add peanuts, green onion and cilantro as garnish and serve with rice.
