Cut the heads and tails off the trout (you can ask your fishmonger to do this for you). Slash each side three times on an angle about half a centimetre deep. This is to allow the flavours to develop and stop the fish from curling up.
Season inside and out and pack the stomach cavity with the butter and herbs. Place in a roasting tin and pour over a splash of white wine and drizzle with a touch of olive oil.
Cover with foil and bake in the oven for approximately 10-15 minutes or until cooked through.
Serve with a few sea salt crystals on the top.
Method for the mousseline of wild brown trout
Place the fish stock, carrot, celery, onion, white wine and seasoning in a saucepan. Simmer to reduce and concentrate the poaching liquor for 30mins.
Add the smoked trout and salmon fillets to the liquor and poach for about five minutes.
Leave to cool slightly, then carefully pick away the flesh, discarding any skin and bones. Reserve half the fish for the pastry and place the remainder in a food processor.
Add the horseradish, cream, softened butter, parsley and egg to the processor and blend until smooth.
Transfer the mixture into 4 x buttered moulds/kilner jars in which the mousse will be presented.
Arrange the moulds/kilner jars into a small roasting tin and half fill with boiling water. Cover with foil and bake in the oven at 170C/325F/Gas 3 for 10-12 minutes, until the mousseline has set.
Method for the trout, spinach and tarragon pastry
First make the sauce. Soften the butter in a small saucepan. Fold in the flour and whisk in the milk a bit at a time until you have a thick white sauce.
Add the tarragon and simmer for about five minutes to cook out the flour and bring out the flavour.
Season to taste and set aside to cool.
When cool, fold in the prawns.
Meanwhile prepare the spinach. In a saucepan melt the butter, add the spinach and gently heat through for a few minutes until the spinach has wilted in the butter and its own vapour.
Strain well then blot the leaves on kitchen roll. It is important that the spinach is as dry as possible.
Roll out the pastry in a rectangular sheet. With the long side closest to you, cover the half furthest away from you with a layer of spinach leaves.
Top with the reserved fish meat.
Cover this with a layer of the tarragon sauce and prawn mixture.
Top with another layer of spinach leaves.
Fold over the pastry and seal with beaten egg so it looks like a giant sausage roll with the ends closed.
Lightly score the top with the back of a knife.
Place on a baking sheet and brush with beaten egg.
Bake until golden in a pre heated oven at 170C/325F/Gas 3 for about 25 minutes, or until golden brown.
Once cooked, cut into slices around 2-3cm thick
Method for the watercress quenelle
Bring a pan of salted boiling water to the boil and blanch the watercress and Chinese cabbage for 2-3 minutes, then drain.
Place the watercress, cabbage and pine nuts into a food processor and add the extra virgin oil. Blitz until loosened.
Add the lemon juice and seasoning and a touch of chicken stock and blitz again until textured but not pureed.
Check for seasoning, transfer to a pan and heat gently.
Method for the dill sauce
Whisk the sugar vinegar and mustard together in a bowl, slowly whisk in the olive oil until smooth and thickened.
Season to taste then add the dill.
Method for the rhubarb compote
Place the rhubarb, sugar and star anise into a sauce pan, and add a splash of water.
Heat for 10-12 minutes on a gentle heat or until the rhubarb has cooked down to a soft puree.
Remove the star anise before serving.
Arrange the mousseline in the kilner jar at the end of a rectangular serving plate and drizzle with the dill sauce. Top with 2 deep-fried sage leaves.
Arrange the poached trout next to the mousseline, with a spoonful of rhubarb compote and a quenelle of watercress alongside.
Finally arrange a slice of the trout, spinach and tarragon pastry on the plate, with a final drizzle of dill sauce over this to serve.