Place the mackerel, lemon juice, horseradish sauce and creme fraiche in a food processor and blitz together. If you don't have a food processor, mix it with a fork. Check the flavours and add more horseradish or lemon according to your own preference.
Empty the pate into a dish and sprinkle with the lemon zest, parsley and a dash of black pepper.
Notes
Storing Smoked Mackerel
Because they have been smoked, mackerel fillets usually have a shelf life of several weeks when you store them in the fridge. You can also freeze the smoked mackerel fillets for up to 3 months. It may say on the packet that you can't freeze them. This is because it is a particularly oily fish and the taste after it has been frozen may change slightly. It will however still be safe to eat. If you do freeze it, try to use it up as soon as possible. You should store Smoked mackerel pate in an airtight container in the fridge. It will keep for 3 days. You can freeze smoked mackerel pate although the texture might change slightly when it is defrosted.