Salmon doesn't need rich cream sauces; just a light, fragrant Thai-inspired broth with the tang of lime juice. Serve with a small bowl of rice per person, or just add some cooked rice vermicelli noodles under the salmon.
Cut the salmon into wide fingers. Finely slice the shallots, chilli and mushrooms. Heat the chicken stock in a saucepan with the shallots, chilli, mushrooms and sugar, and simmer for 10 minutes.
In the meantime, heat the oil in a nonstick frypan and sear the salmon skin-side down for most of its cooking time, turning once, leaving the inside pink. Season with salt and pepper.
Using tongs to hold the spinach, wilt it in the hot broth for 10 seconds, then arrange in four warmed shallow soup or pasta bowls. Place the salmon on top. Add the fish sauce, lime juice and diced tomato to the broth and spoon it around the salmon. Scatter with coriander sprigs and serve.