Whack the lemongrass against your work surface and remove the tough outer layer. Peel the ginger, then very finely chop with the inside of the lemongrass and most of the coriander, stalks and all, reserving a few nice leaves in a bowl of cold water. Chop the salmon into 1cm chunks over the mix on your board, then push half the salmon to one side. Chop the rest until super-fine, almost like a purée, then mix the chunkier bits back through it and season with sea salt and black pepper. Divide into 4, then shape and squash into 2cm-thick patties.
Place a large non-stick frying pan on a medium-high heat with 1 tablespoon of olive oil. Cook the patties for 2 minutes on each side, or until nicely golden. Spoon the chilli jam over the fishcakes, add a splash of water to the pan, turn the heat off, and jiggle to coat. Serve sprinkled with the drained coriander.