Smoked mackerel and quick-pickled shallot toasts

Method

1. Put the shallots in a small heatproof bowl. Heat the vinegar, caster sugar and salt in a saucepan until the sugar has dissolved and the mixture is steaming, then pour it over the shallots in the bowl. Stir to mix, then leave to pickle for at least 45 minutes or up to 24 hours.
2. Drain the shallots and set aside. Lay the bread on a large baking sheet along with the smoked mackerel fillets. Put the baking sheet under a medium-high grill for 3-4 minutes until the bread is lightly toasted, flip the bread and the fish fillets and grill for 2-3 minutes more, then leave to cool. Once you can handle the mackerel, cut or flake into small chunks to fit on the bread squares.
3. Combine the horseradish, crème fraîche and garlic in a bowl and season with salt and pepper. Spread a little of the mixture over the slices of toast, then top with a pieces of smoked mackerel. Add a few rings of shallot on top, grind over a little black pepper, then serve immediately while still warm.