Method – Combine all ingredients in a bowl, cover, refrigerate and leave for 1 hour. Heat bread slices in a 180c degree oven for 5-10 minutes until dry and crisp but not browned. Top bread with mackerel mixture and finish with a slice of cucumber and a grind of black pepper.
Recipe from: http://www.nibbledish.com/people/felders/recipes/mackerel-tartare-toasts
Changes were made. http://creativecommons.org/licenses/by-sa/3.0/