Have four slices of your favourite bread ready toasting under the grill.
Peel the skin off the mackerel and flake into a bowl.
Add four tablespoons of double cream, grate in 50g/2oz of parmesan, add a pinch of black pepper and mix with a fork.
Add a spoonful of chopped chives and some grated horseradish, and mix again.
Pile the mixture onto the toast.
Add a final drizzle of cream and a scattering of grated parmesan and put them under the grill for 3-4 minutes.
Serve when they start to bubble and brown.
