Potato and pea curry with tomato and coriander (aloo dum)

INGREDIENTS

• 1kg/2lb 4oz potatoes
• 4 tbsp mustard oil or vegetable oil
• 1 tsp ground turmeric
• 3 tbsp vegetable oil
• 2 Indian bay leaves
• ¼ tsp asafoetida
• 1 medium onion
• 6 garlic
• 5cm/2in fresh root ginger
• 1 tsp Kashmiri chilli powder
• 1 tsp ground cumin
• 1 tsp ground coriander
• ½ tsp amchur (dried mango powder)
• ½ tsp ground turmeric
• ½ tsp salt
• 200g/7oz tomato passata
• 2 green chillies
• 150g/5½oz frozen peas
• 1 tsp garam masala
• handful chopped coriander