Vietnamese lamb burgers with pickled vegetables

Ingredients

• 1 x 500g pack (20% fat) lamb mince
• ½ lemongrass stalk, very finely chopped
• 2 garlic cloves, chopped or crushed
• 1 red chilli, deseeded and finely chopped
• 1 tbsp chopped mint
• 2 tbsp chopped coriander
• 1 tbsp Thai fish sauce
• 1 small red onion, thinly sliced
• 100ml rice vinegar
• 3 tbsp caster sugar
• 2-3 garlic cloves, finely chopped
• juice of 1 lime
• 2 tbsp Thai fish sauce
• ¼ cucumber
• 6 radishes
• 4 seeded burger buns
• round lettuce leaves
• coriander sprigs