For the filling
1 Tbsp grapeseed oil
60g banana shallots, peeled and finely diced
1 tsp garlic puree
30g chestnut mushrooms, finely diced
30g unsalted butter
200g baby spinach
4 g tarragon leaves
salt and freshly ground black pepper
For the herb pancakes (makes 4-6)
25g baby spinach (blanched and drained weight)
3g tarragon leaves
4f flat leaf parsley
75g plain flour
100g whole milk
To finish the salmon
2 x 250g sheets ready-rolled puff pastry
reserved herb pancakes
500g salmon fillet, skinned and deboned
1 egg, lightly beaten
To make the filing, heat the grapeseed oil in a pan and cook the shallots over medium heat until softened. Add the garlic and mushrooms cook for an additional 2 minutes. Remove from the heat and set aside to cool. In a separate pan, melt the butter over moderate heat and add the spinach leaves, stirring continuously until completely wilted and cooked. Drain the spinach in a mesh sieve and place into a container. Once cooled, squeeze out as much liquid as possible from the spinach using the back of a spoon and then pat dry with kitchen paper. Add the spinach to the mushrooms mixture and combine well. Finely chop the tarragon leaves and add to the filling, seasoning well with salt and freshly ground black pepper. Cover and set aside until needed.
For the herb pancakes, boil the spinach in a pot of boiling water for 30 seconds, then remove and plunge into an iced bath. Once cooled, drain and squeeze out excess liquid, then pat dry with kitchen paper. Roughly chop the spinach and add to a blender with the remaining pancake ingredients. Blend on high until smooth. Pass the batter through a sieve and set aside. Lightly grease a non-stick pan with a dab of olive oil and cook the pancakes one at a time over low-moderate heat. Set aside until needed.
To finish, roll out one of the puff pastry sheets onto a sheet of parchment paper. Place two pancakes on top of the pastry and spread half the mushroom filling out onto the pancakes. Place the fillet of salmon on top and cover with the remaining filling. Top with two more pancakes and wrap well. Brush the visible areas of the bottom layer of pastry with egg wash and cover the salmon with the second sheet of puff pastry. Trim the pastry around the edges and use a fork to decoratively seal the pastry. Place in the fridge until needed.
To cook, preheat the Furnace BBQ to 210°C - with the pizza stone placed above the grill. Place the salmon (still on the parchment paper) onto the pizza stone and cook for 30 minutes ensuring the temperature of 210°C is being maintained. The salmon should reach a core temperature of 50°C when probed, before it is removed. The temperature will continue to rise once the salmon is resting. Rest for 10 minutes before serving.