Peel the onion and cut into small cubes. Peel the limes thickly, remove the white membranes from the fillets and cut them into pieces. Heat 2 tbsp. oil in a frying pan. Sauté onion and lime fillets in it. Add brown sugar and curry powder, continue to sauté for 2 min. Add the whipped cream and simmer for about 15 minutes. Grind the lime sauce, then pass it through a fine sieve. Season to taste with salt and freshly ground pepper. Rinse the pike-perch fillets, dry them, season with salt and season with pepper. Heat 6 tbsp of oil in a frying pan, roast the fish pieces in it for 3-4 min per side. Remove the fish and keep warm in the oven.
Remove skin from sweet potatoes or potatoes, rinse, and slice with a peeler. Heat frying oil in a saucepan or deep fryer. Fry the potatoes in batches until golden brown. Drain the chips on kitchen paper and season lightly with salt. Serve the pike-perch fillets with the lime sauce and the chips. Serve garnished with peanuts, coriander greens and perhaps lime fillets.