Boil the sweet potatoes and cumin seeds in water until tender.
Drain and mash potatoes with butter, cream, salt, and pepper.
Heat olive oil in a frying pan and fry the halibut for 3-4 minutes per side.
Add lemon juice to the pan with the halibut.
Simmer white wine, cream, lemon juice, and mustard in a saucepan for two minutes.
Stir chopped chives into the cream sauce.
Stir-fry garlic and chilli powder in oil for one minute.
Add broccoli to the pan and fry for three minutes.
Mix in tomatoes and cook for one further minute.
Plate the mash with fish on top, drizzle with sauce, and serve with broccoli.