Ingredients  
1 x 320g packet of ready rolled puff pastry 
500g Salmon fillet 
125g Mascarpone 
75g full fat crème fraîche 
15g chives, finely chopped 
1 tbsp lemon 
Salt 
Pepper 
A small egg beaten

Method  
Preheat the oven to 200c. 

Mix the mascarpone, crème fraîche, chives and seasoning (I like ½ tsp of salt and a good grinding of black pepper but you do need to season according to your taste buds so mix it and then taste). 

Hopefully your puff comes on baking paper and not plastic but if it does not then I find the easiest thing to do is to is to unroll the pastry placing it directly on to a piece of baking paper, it is easier to pick up on the baking paper than trying to lift the pastry from your work surface. 

Put the salmon on the pastry and leave an edge of at least 3cm.  Take the egg or milk - whatever you are using - and brush it on the pastry around the edge of the salmon fillet.  Top the salmon with the cream mix and neaten by pushing it down evenly.  Fold the pastry over the top.  Push the two sides of the pastry together (the egg or milk should glue the two sides together) and cut the pastry to fit around the salmon leaving an overhang of 3cm all around.     

Put into the oven for 25-30 minutes until your pastry is golden all over.  The easiest way to check if your salmon is hot in the middle is to stick a metal skewer or sharp knife into the centre of the salmon and hold for 5 seconds or so.  Take the skewer and very carefully hold against your finger, it should be hot.