Lamb madras with bombay potatoes

Ingredients

• 1 x 2.5kg/5½lb shoulder of lamb
• 1 tbsp olive oil
• 2 tbsp coriander seeds
• 2 tbsp fenugreek seeds
• 1 tbsp mustard seeds
• 1 tsp cumin seeds
• ½ tsp fennel seeds
• 1 tsp black peppercorns
• 1 cinnamon stick
• 5 cloves
• 1 tbsp ground turmeric
• 1 green bird’s-eye chilli
• 2 garlic cloves, peeled
• 1½cm/¾in root ginger, peeled
• 1 onion, thinly sliced
• 2 tbsp vegetable oil
• 12 curry leaves
• 3 cardamom pods
• 2 bay leaves
• 400g/14oz chopped tomatoes
• 200ml/7fl oz beef stock
• 2 tsp tamarind paste
• salt
• freshly ground black pepper
• 500g/1lb 2oz potatoes, cut into 2cm/1in cubes
• 4 tbsp vegetable oil
• ½ tsp mustard seeds
• ½ tsp chilli powder
• ¼ tsp ground turmeric
• 2 tbsp fresh coriander, roughly chopped