Smoked Haddock & Leek Gratin with Seeded Crumb Topping

Heat the oven to 180°C fan / 200°C conventional. Melt the butter gently in an approximately 20cm non-stick saucepan. Add the leeks and 3 tbsp water, cover and cook gently for 6–8 minutes until soft. Stir occasionally; add another splash of water if they catch.

Stir the flour into the soft leeks and cook for 1 minute. Gradually stir in the milk, then simmer gently for 2–3 minutes until lightly thickened. Remove from the heat and stir in the crème fraîche, mustard, lemon juice, half the parsley and the pepper.

Put the spinach in a colander and pour over a kettleful of boiling water. Let it cool enough to handle, then squeeze out excess moisture and roughly chop. Fold it into the leek sauce. Check the haddock for bones again and fold in the raw fish chunks.

Transfer to an approximately 20 × 15cm shallow baking dish (about 750ml capacity). Scatter the fresh seeded crumbs evenly over the top; the bread’s own seeds and fat help them toast, so no extra oil is needed. Bake for 20–25 minutes until bubbling at the edges, the topping is golden and the fish flakes easily. Check the centre is piping hot and reaches 70°C for 2 minutes, or 75°C for 30 seconds. Cover loosely if the top colours early.

Rest for 3 minutes, scatter over the remaining parsley and divide the complete gratin equally between two plates or shallow bowls. The full sauce and topping belong in each serving.