Process parsley, shallots, capers, lemon rind and juice in a small food processor until finely chopped. Add one piece of avocado and pulse to form a paste.
Heat a medium non-stick frying pan over a medium-high heat. Add salmon. Cook for 3 minutes. Turn and cook for a further 3 minutes or until cooked to your liking. Remove and flake into large pieces.
Meanwhile, cook spaghetti in a medium saucepan of boiling water following packet directions. Reserve ¼ cup pasta water, then drain.
Transfer spaghetti and reserved pasta water to a medium bowl. Add flaked salmon, avocado mixture, olives and rocket leaves. Season with freshly ground pepper and toss gently to combine.
Divide into 2 serving bowls. Top with remaining thinly sliced avocado. Sprinkle with pine nuts.

Salmon can be replaced with 480g skinless chicken breast fillets, if preferred. Cook chicken in a large non-stick frying pan over a medium-high heat for about 5 minutes on each side or until cooked through, then slice thinly. Or, for a shortcut, skip step 2 and stir through 450g shredded, skinless cooked chicken breast in step 4.