Fry leek in butter until wilted, then add lemon zest and juice, cornflour paste and Thai fish sauce. Stir until thickened, then gently mix in scallops, fish and spring onions. Check seasoning, adding salt and pepper if needed. Place mixture in a lightly buttered
Roughly spread the mash on top of the fish, if you make it too smooth it won’t have that lovely rustic look that gives a crunchy texture.