Preheat the oven to 200C/400F/Gas 6.
Place the oil into a large, deep roasting tin, until ithe oil is 2cm/1in deep in the tin and place into the oven until smoking.
Carefully add the potatoes to the hot oil and turn them in the oil to coat. Season with salt and freshly ground black pepper and place into the oven for ten minutes.
Carefully add the crushed garlic, tomatoes, chillies and paprika to the potatoes and stir to combine. Return to the oven to roast for a further 30 minutes, or until the potatoes are crisp on the outside, but soft on the inside.
Season, to taste, with salt and freshly ground black pepper, add more olive oil if the potato mixture has become dry and sprinkle with the parsley.
For the hoki, lightly oil a clean roasting tray and add the hoki steaks. Season lightly with salt and freshly ground black pepper and squeeze lemon juice over the top.
Place the cheese, mustard and beaten egg into a bowl and stir well to combine.
Divide the cheese mixture into ten portions and mould each portion to fit on top of a piece of the hoki, then press onto each of the fish steaks. (Don't worry if it looks a bit sloppy: the egg will set the topping when it cooks.)
Transfer the fish to the oven and roast for 10-15 minutes, or until the cheese browns and the fish is completely cooked through.
To serve, press a spoonful of patatas bravas onto a plate, then place a hoki steak on top.