Ingredients

Steps

• Place cucumber slices in a colander, sprinkle with salt, and drain for 30 minutes.
• Rinse cucumbers with cold water, drain, and wring out excess moisture.
• Mix horseradish with crème fraîche and mustard powder in a bowl until smooth.
• Season mackerel fillet skins with salt and black pepper.
• Fry fillets skin-side down in foaming butter under a heat-proof plate for 5 minutes.
• Turn fillets and cook for 30 seconds until just done.
• Assemble by layering cucumber, mackerel, horseradish sauce, onion, and lemon on buttered toast.