Salmon Wellington with White Wine Sauce

20 g butter
1 tsp rice bran oil
2 shallots, finely chopped
300 g mixed mushrooms, finely chopped
120 g mascarpone
Finely grated zest of 1 lemon
2 tbsp each chopped tarragon
2 tbsp chopped parsley
2 tbsp chopped chives
2 sheets frozen butter puff pastry, thawed
1 kg skinless centre cut salmon fillet, pin-boned
1 egg, lightly beaten with 1 tsp cold water
Rocket leaves, to serve
WHITE WINE CREAM SAUCE:--
50 g cold butter, chopped, plus 15 g extra
1 shallot, finely chopped
150 ml white wine
200 ml fish stock
100 ml thickened cream
SIDS SALT & PEPPER to taste
1 tbsp chopped parsley
1 tbsp chopped chives

Heat 50 g butter and oil in a frypan over medium heat. Add shallot and cook, stirring, for 2 minutes, then add the mushroom and cook for 10-12 minutes until all liquid has evaporated from the vegetables. Cool completely, then stir in mascarpone, lemon zest, herbs. Season with SIDS SALT & PEPPER.
Preheat oven to 200°C. Line a baking tray with baking paper.
Place 1 pastry sheet on prepared tray (leave the 2nd sheet in the fridge to keep cool) and prick all over with a fork. Bake for 20 minutes until crisp and golden. Remove from oven and cool completely. Remove remaining pastry from the fridge.
Spread half the mushroom mixture over the cooled pastry base, leaving a 5 cm border, and place salmon on top. Spread remaining mushroom mixture over top and sides of salmon and drape over the 2nd sheet of pastry, tucking under pastry base. Brush all over with egg wash and chill for 30 minutes.
Remove Wellington from the fridge and bake for 30-35 minutes, then reduce oven to 180°C and cook for a further 10 minutes until the pastry is crisp and golden. Remove from oven and rest for 10 minutes before serving.
WHITE WINE CREAM SAUCE: melt extra 15 g butter in a pan. Add the shallot and white wine then bring to the boil. Cook for 4 minutes until reduced by ⅓, then add the stock and cream and bring back up to a boil. Reduce heat to medium-low and simmer for 8-10 minutes until reduced and thickened. Using a whisk add the cold butter 1 cube at a time, whisking in between each addition until completely emulsified. Season with SIDS SALT & PEPPER and stir in the chopped chives and parsley.
Carve Wellington into slices and serve with the cream sauce and rocket leaves.