1. Sous vide the salmon in a 42°C water bath for around 30 minutes.
2. Pour the coconut milk into a sauce pan, add the soya and fish sauces and bring the mixture to simmering point. Add the ginger, lemongrass, lime leaves and onion to the milk, and simmer for 10 minutes, until the liquid infuses with the flavours and the onion softens.
3. In the meantime, prepare the noodles by soaking them in hot water for 8-10 minutes, until they become soft.
4. To serve the dish, put the noodles in the bowls, top with the salmon, herbs and cucumber and pour the liquid over them. Squeeze some lime juice and sprinkle some chili and voilà!