Heat oil in a deep-fryer or large saucepan to 190 degrees C.
Beat the egg into a shallow bowl with a tablespoon of water. Place the bread crumbs in a shallow bowl. Dip the fish pieces into the beaten egg and then into the crumbs until well coated. Fry the fish nuggets in batches, about 1 minute on each side. Drain on paper towels and set aside.
Heat the olive oil in a frypan or Dutch oven over medium heat. Stir in the onion and capsicum strips; cook and stir until the onion has softened and turned translucent, about 5 minutes.
Coarsely crush the anise seed. Add the anise seed, tomato paste and chopped tomatoes to the frypan and cook, stirring frequently, until the tomato paste has darkened and the tomatoes have softened, about 5 minutes.
Chop the lemon wedge, peel and all, into five pieces. Stir the lemon wedge and crushed garlic into the tomato mixture and cook for 1 minute more. Mix in 1 cup (250ml) water, salt and pepper, cayenne pepper, brown sugar and olives. Bring the sauce to a boil and simmer for 20 minutes. Stir in more water if the sauce gets too thick. Gently stir in the fish nuggets, and simmer for an additional 10 minutes.