Make your green salt crust: In a food processor add the stalks of your herbs, reserving the leaves. To this add a handful of your sea salt and the zest of the 2 limes. Pulse this until it forms a fairly smooth, bright green puree. Tip this mixture into a large bowl with the remaining salt and your egg whites and mix together. Slice the limes and set aside.
Make your yellow salt crust: Take one of your sticks of lemongrass and remove the tough outer layer, then finely chop the rest. In a food processor add the turmeric, grated ginger, chopped lemongrass and lemon zest with a handful of the sea salt. Pulse this together until it forms a smooth, yellow paste. Tip this mixture into a large bowl with the remaining salt and your egg whites and mix together. Take your second stick of lemongrass and lightly bash it, again removing the tough outer layer. Slice the lemon and set aside.
Encase your fish: Preheat your oven to 210C. Line a baking sheet with baking parchment.
Using your chose salt crust, place ½ of the mixture on the baking tray in the shape of your fish. Lay your sea bream (or whichever whole fish you choose to use) onto the salt. Lifting up the top side of your fish fill your cavity with either the herbs and slices of lime for your green salt crust or the lemon slices, ginger slices and lemongrass for your yellow one. Season the inside with black pepper. Encase the top of the fish with the remaining salt crust, leaving the head and tail exposed. Pat the salt mix well into the fish ensuring there are no gaps.
Bake your fish in the middle of the oven for 20 minutes. Remove from the oven and allow to rest for 10 minutes.
Carefully break away the salt crust to reveal the delicious succulent fish. Serve alongside new potatoes and fresh steamed spring greens for an impressive dinner.