Fill a large pan with boiling water. Bring back to the boil. Scrub the potatoes. Halve or quarter them so they’re roughly the same size. Add the potatoes to the pan. Simmer for 5 mins. Drain well.
While the potatoes cook, peel and finely slice the onion. Peel and crush the garlic.
Warm 1 tbsp oil in a deep frying pan or wok. Add the parboiled potatoes. Fry over a medium heat, stirring now and then, for 5 mins till the potatoes are golden and starting to crisp up at the edges.
Add the onion to the pan. Fry for 5 mins, stirring, till the onion is glossy and golden and the potatoes are golden brown.
Add the garlic to the pan. Measure out 1 tsp each of the smoked paprika, fennel seeds and cumin seeds. Add them to the pan. Cook and stir for 1 min till the pan smells sweet.
Stir in the tomatoes. Season. Place the hake fillets in the pan. Cover and simmer for 8-10 mins till the hake is opaque and cooked through. It should flake easily when you press it with a fork.
Lift the hake out of the pan and put it on warm serving plates. Taste the tomato sauce and adjust the seasoning. Serve the veg with the hake, garnished with the parsley leaves.