Line a half-pipe shaped 1lb tin with a double layer of clingfilm, making sure it overhangs the edges.
Line the lined tin with the slices of smoked salmon, making sure that you have an even double layer of smoked salmon; let the edges hang over the edge as they will be folded back over the filling.
Combine the cream cheese and the goat's cheese in a large mixing bowl.
Beat until smooth, then add the chopped chives, lemon juice, 40g of roughly chopped pistachios and the diced avocado and fold until incorporated.
Spoon into the tin on top of the smoked salmon, smoothing the top with a knife.
Bring the overhanging pieces of smoked salmon over the filling and wrap the double layer of clingfilm that is overhanging over the top.
Chill for 2-3 hours.
When you want to serve the roll, remove it from the fridge and unwrap.
Use the underneath layer of clingfilm that you used to line the tin to help remove it.
Invert the flat side onto a plate and slice into thin portions.
Garnish the top with the roughly chopped pistachios.