Combine soy sauce, garlic, five spice and sugar in a jug. Place salmon and mushrooms in separate ceramic bowls. Pour half marinade over each, stir to coat.
Cover and refrigerate for 2 hours. Preheat a barbecue plate or non-stick frying pan over high heat. Drain salmon, discard the marinade. Cook salmon for 2 - 3 minutes each side or until cooked to your liking. Transfer to a plate, cover to keep warm.
Add Asian greens, capsicum, bean sprouts, coriander and mint to the marinated mushrooms, toss to combine. Flake the salmon fillets and add to the salad with sweet chilli sauce. Toss gently to combine. Serve with extra sweet chilli sauce if desired.