1 large leek, thinly sliced
1 lemon, zest and juice
4 spring onions, thinly sliced
1 tbsp fresh thyme leaves
160g/5戮oz short pasta, such as penne
salt and freshly ground black pepper
1 tbsp olive oil
25g/1oz butter
3 tbsp full-fat cr猫me fra卯che
2 x 120g/4录oz salmon fillets, skin removed