Based on this recipe.

cost: £2 serves: 2-4
serve on smaller croutons or crackers as a starter or appetizer

2 fillets smoked mackerel
100 ml crème fraîche or soured cream
1 T horseradish
half a lemon
black pepper
1 small bunch spring onions chopped

Remove the skin from the mackerel and place in a bowl. Flake apart with a fork, then stir in the cream, horseradish, and the juice of half a lemon. Add black pepper and spring onions and mix. Serve on freshly toasted bread for a light meal.