Place the oil into a frying pan over a medium heat. Add the black pudding rounds and fry, turning once, until crisp on both sides, then set aside.
Add the butter to the pan and, once foaming, add the onions and fry for three minutes, or until soft.
Add the rice and stir well to coat the grains in the butter and the onion.
Add a ladleful of stock and stir the rice well. When the stock has been absorbed by the rice, add more and continue stirring, adding more stock as it is absorbed until the rice is cooked. You must stir the rice constantly until it is cooked, which may take up to 40 minutes.
Add the curry powder to the cooked rice and stir well.
Break up the smoked mackerel fillets into flakes (removing any bones you might discover) and add to the rice mixture.
Add the eggs, cooked black pudding and coriander and stir gently to combine.
Break up the mackerel fillets, removing any bones, and sprinkle the flakes over the top of the dish.
To serve, place a few generous spoonfuls of kedgeree into bowls and garnish with a little freshly grated nutmeg.