Skin and de-bone the Mackerel (if the fish is already filleted double check there are no bones).
Using a fork, flake the fish.
Place the fish in a food processor / blender, along with the cottage cheese, lemon juice and sour cream.
Blend into a smooth consistency then pour the mixture into a bowl.
Add the nutmeg, salt and pepper and mix (add more lemon juice if necessary)
Place the mixture into a serving container and cover with tin foil.
Chill in the fridge for no less than two hours, and for a maximum of one day.
Sprinkle with cayenne pepper before serving.