In a large bowl, mix the flour, baking powder and salt until well combined. Add the butter and work it in until it has the consistency of breadcrumbs. Gradually add a few tablespoons water until it forms a thick dough. Work it with your hands until smooth and well combined. Set aside.
In a pot or saucepan, place the fish, garlic and the whole ginger without chopping it. Add half of the onion along with the Maggi cubes, curry powder, parsley, salt and some pepper to taste. Add the fish stock and enough water so the contents of the pot are almost covered.
Bring to the boil and cook for about 20 minutes until the fish is soft and tender.
Remove the fish from the pot and place in a bowl. Using a fork or your hand, crush the fish until it is in small bits and leave to cool.
Heat a few drops oil in a frying pan. Add the rest of the onion and chillies and fry until soft. Add the fish and fry for a few minutes. Add some of the stock from the fish and cook until heated through, about 2 minutes.
Chop up the cabbage and carrots and add them to the fish mixture. Cook for 5 minutes on a low heat then add a few teaspoons of flour and stir well. Turn off the heat.
Preheat the oven to 180 C / Gas 4.
Flour a work surface and roll out the pastry. Cut out circles with a glass and spoon some of the mixture unto each circle. Fold the edges over and seal it with a fork. Arrange the pieces on a baking tray lined with baking parchment. Brush each circle lightly with the egg yolk.
Bake in the preheated oven until light brown at the top, 15 to 20 minutes.
Be careful not to add too much water to the pastry so it won't get sticky. But if it does, place in the fridge for about 30 minutes.
Instead of carrots, you can use any vegetable mix you like.