Dried basil seeds are available from Asian supermarkets. When soaked in water they swell and become gelatinous. They add texture to the drink but no flavour.
565 g (1 lb 4 oz) tin lychees in syrup
270 ml (9½ fl oz) coconut milk
115 g (4 oz/½ cup) caster (superfine) sugar
1 lemon grass stem, white part only, bruised
grated zest and juice of 1 lime
200 g (7 oz/¾ cup) plain yoghurt
1 teaspoon dried basil seeds, optional
lime wedges, to serve
1. Drain the lychees, reserving 150 ml (5 fl oz) of the syrup as well as the lychees. Put the syrup in a saucepan and add the coconut milk, sugar, lemon grass and lime zest. Stir over medium heat until the sugar has dissolved. Bring to the boil, then reduce the heat and simmer for 1 minute. Remove from the heat and set aside to infuse for 15 minutes.
2. Strain the mixture into a blender and add the reserved lychees and yoghurt. Whizz for 30 seconds, or until smooth. Add the lime juice and whizz until just combined. Refrigerate until very cold.
3. When ready to serve, put the basil seeds, if using, in a small bowl and cover with water. Set aside for 3–4 minutes, or until the seeds have swelled. Stir the lassi, then pour into four glasses and top with the basil seeds. Serve with lime wedges, if desired.