I've used lemongrass in this tuna dish, which was inspired by a beef rub used in traditional Vietnamese jungle beef salads. You can eat this as hand-held morsels, or pile the herbs and dressing onto the tuna and serve it as a salad.
1 thick lemongrass stem, pale end finely sliced
3 garlic cloves, chopped
½ tsp Chinese five-spice
1 tbsp salt flakes
½ tsp freshly ground black pepper
700g mid-loin tuna, trimmed and cut lengthways into two pieces
80ml grapeseed oil
1 white salad onion, finely sliced in half-moons
1½ tbsp basil seeds, soaked in cold water for 20 minutes and drained
1 lemon, peeled, segmented and chopped
4 hard-boiled egg yolks
½ bunch Thai basil, leaves picked
½ bunch dill fronds, leaves picked
½ bunch coriander, leaves picked
½ bunch Vietnamese mint, leaves picked
2 handfuls lemon balm, leaves picked
2 long green chillies, finely sliced
lime wedges, to serve
black sesame crackers or large prawn crackers, to serve
superfine rectangles of rice paper, cut into triangles, to serve (if these are hard to find you could just use the prawn crackers or lettuce cups, or try lightly moistening spring roll wrappers with a damp cloth)
4 small garlic cloves, chopped
4 red bird's eye chillies, chopped
3 tbsp lime juice
3½ tbsp Vietnamese fish sauce
3 tbsp white sugar
1. Pound the lemongrass and garlic using a mortar and pestle until an even paste. Add the five-spice, salt and pepper and combine. Smear the paste evenly over the tuna, pressing it on firmly.
2. Add the oil to a frying pan over medium heat and sear the tuna pieces evenly for about one minute on each side. Set aside to cool, and then wrap tightly in cling film. Refrigerate until chilled.
3. For the dipping sauce, pound the garlic and chilli using a mortar and pestle until a rough paste. Add the lime juice, fish sauce and sugar and mix until the sugar has dissolved. This will need to sit for about five minutes before using.
4. Once chilled, cut the tuna into slices about five millimetres thick – don't slice it too thinly – and arrange on a serving platter. Top with the onion, basil seeds and chopped lemon and grate over the egg yolks. Combine the herbs and green chilli and pile onto a platter with the dipping sauce, lime wedges, rice paper and crackers on the side. Drizzle some of the sauce over the tuna and serve.