Place the salmon fillets onto a baking tray with a rack, sprinkle both sides with the fine sea salt and leave in the fridge until ready to cook.
Toast the walnuts in a dry pan until golden brown and fragrant.
Blanch the spinach leaves in boiling water for 20 seconds then cool in an ice bath to stop them cooking. Squeeze out excess moisture once cooled.
To make the pesto, add the parmesan, basil, walnuts, garlic, spinach, salt and pepper into a blender. Blitz until smooth.
Add the leeks, butter and oil into a pan. Cook for 5 minutes over a medium-high heat until softened and starting to caramelise.
Add the Orzo and stock, bring to a simmer, then cover and cook for 15 minutes on low heat. Add an extra splash of water if needed halfway through.
Once the orzo is cooked, remove from the heat and stir in the pesto. Mix together well.
Remove salmon from the fridge then pat the skin dry.
Add some oil o a frying over a high heat, then lay the salmon in skin side down. Press down on th salmon, turn heat down to medium-high then cook for 5 minutes until crisp and brown. Flip the salmon, sear the flesh for 2 minutes, then set aside.
To serve, add the salmon on top of a bowl of orzo with a dollop of sour cream, freshly chopped dill and some lemon zest and juice.