Soak snoek in water for 1 hour. Drain, cover with fresh water and boil until cooked, about 15 minutes. Meanwhile, braise onions in heated oil until quite brown, about 10 minutes. Add cabbage and garlic, and cook, covered, until cabbage is lightly browned, about 15 minutes. Add chilli and sugar. Add potatoes and simmer, covered, until potatoes are cooked, about 15 minutes.
Drain and flak