2 sticks of lemongrass
a small, hot, red or yellow chilli
a walnut-sized piece of ginger
4 tbsp fish sauce
2 tbsp caster sugar
1 tbsp flavourless oil, such as groundnut or vegetable oil
small bunch coriander leaves
few bushy sprigs of basil
4 mackerel fillets
Finely slice 2 sticks of lemongrass. Seed and finely chop a small red or yellow chilli, and peel and grate a walnut-sized piece of ginger.
Slice 4 limes in half, and squeeze them into a bowl. Pour in the fish sauce and stir in the caster sugar.
Get a wok hot and then pour in the vegetable oil. Add the lemongrass, onions, chilli and ginger and stir-fry them briefly. They should soften rather than colour. Pour the lime juice mixture into the wok then scatter on the coriander leaves and basil.
Place the mackerel filets skin-side down on a grill pan. Place them under a hot grill until the flesh turns opaque. Remove the pan from the heat and spoon the aromatic topping onto the fish. Return to the grill for 5 minutes or so until the mixture starts to brown. Serve at once.