For the Arbroath Smokie purée
Place the smokies in a moderate oven for 10 minutes. Remove from the oven, take off the skin and remove all of the bones. Set some larger flakes aside for the garnish.
Place the bones and skin in a pan with the fish stock, cover with a lid and return to the oven. Cook for 20 minutes, strain and reduce by half. Place the fish flesh into a blitzer and process until a light dropping consistency by adding some stock. Keep warm.
For the sauce
Place the butter shallots and garlic into a pan and sweat until tender. Add about 140ml chicken stock and reduce into a light syrup. Continue until the last 175ml remain; add the cream and mustard. Bring to the boil, strain and check the seasoning. Keep warm. Add the cream and mustard. Bring to the boil, pass and retain.
For the soufflé
Preheat the oven to 220°C/425°F/Gas mark 7. Double butter the soufflé moulds then line with the breadcrumbs. Sweat the shallots in butter and stir in the flour. Cook out the roux until blond. gradually add the warmed milk to a coating consistency. Add the horseradish and cheddar cheese. Leave to cool slightly and add the fish purée, chives, half the lemon juice, egg yolks and correct the seasoning. Whisk the egg whites into soft peaks and rain over a pinch of salt and the remaining lemon juice. Finish whisking into stiff peaks. Cut the egg whites through the soufflé mix and place into the moulds. Place in a warm bain-marie and cook for 10-12 minutes. Allow to drop and cool for 5 minutes in the moulds. Turn out gently onto greaseproof paper.
Lightly thicken the sauce with cold butter. Cover the bottom of an ovenproof dish with the sauce. Place a large spoon of the smokie flakes on the bottom, top with the soufflé and bake at 180°C/250°F/Gas mark 4 for 8 minutes.