Dosa with spiced potato filling

Dosa

• 250 g long grain rice
• 100 g split black lentils (urad dal - see Tips)
• 600 g water, plus extra for soaking
• 30 g cooked rice (see Tips)
• 1 tsp salt

Spiced potato filling

• 1 bunch fresh coriander, leaves only
• 500 g water
• 750 g potatoes, peeled and cut into cubes (2 cm)
• 2 garlic cloves
• 3 cm piece fresh ginger, peeled
• 1 fresh long green chilli, deseeded if preferred
• 1 tsp yellow mustard seeds
• 1 tsp cumin seeds
• ½ tsp ground turmeric
• 60 g ghee, plus extra for frying
• 1 red onion (approx. 120 g), cut into thin slices
• 10 fresh curry leaves
• ½ tsp salt
• 120 g fresh baby spinach leaves