Preheat the oven to 180°C.
Grate the potato into a tea towel and squeeze out all excess moisture.
Season the fish and press the grated potato onto one side of the fillet.
Fry the fish potato-side down in olive oil for 4 minutes until golden.
Flip the fish, add butter, and roast in the oven for 4 minutes until cooked.
Melt butter in a saucepan and sauté onions for 5 minutes until softened.
Add wine and boil until the liquid is reduced by half.
Stir in the cream, season, and simmer until the sauce thickens slightly.
Boil the broccoli florets in salted water for 6 minutes, then drain.
Sauté broccoli in a hot wok with soy sauce, sesame oil, and sesame seeds.
Plate the broccoli, top with the haddock, and finish with the butter sauce.