Heat the oils in a wok and fry the mustard seeds until they start to pop, then add the curry leaves and fry until crisp, about 30 seconds.
Add the onion and saute over medium heat until it starts to colour, stirring constantly. Add the spices, stir to combine and cook for a minute until fragrant.
Slice the okra in half diagonally, removing the tops. Add the okra, garlic and chilli to the pan and saute gently for 10 minutes, until the okra is soft. Season with salt to taste. The sauce should be quite thick.