Pulse herbs, garlic, and chillies in a blender until soft, then store in fridge covered with oil.
Simmer tamarind, spices, sugar, dates, and 200ml water until thick and glossy.
Whisk yogurt with sugar, salt, and 5 tablespoons of water to thin.
Fry onions in oil until golden, then brown the lamb mince for 3 minutes.
Stir in spices, sugar, raisins, cashews, potato, peas, chillies, and ginger for 4 minutes.
Add mint and lemon juice to the filling and cool completely.
Rub oil into flour and spices, then knead with 4 tablespoons of water into a smooth dough.
Divide dough into 12 parts and roll each into a 10cm circle.
Halve circles, form cones using water to seal, and fill with lamb mixture.
Deep fry samosas at 180°C in batches until golden brown.
Drain on kitchen paper and serve with prepared chutneys and yogurt dressing.