Amazing Indian dosa

INGREDIENTS

• 2 baking potatoes, scrubbed
• 2 sweet potatoes, scrubbed
• olive oil
• 1 dried red chilli, finely sliced
• 1 fresh red chilli, finely sliced
• 1 cm piece fresh ginger, peeled and finely sliced
• 1½ teaspoons mustard seeds
• 1 teaspoon turmeric
• sea salt
• freshly ground black pepper
• 1 lime, halved
• 4 spring onions, trimmed and finely sliced
• a few sprigs coriander, roughly chopped
• minted yoghurt, to serve
• Indian chutney, to serve
• lime wedges, to serve
• 1 cup gram (chickpea) flour
• 1 cup flour
• ½ teaspoon bicarbonate of soda
• 2½ teaspoons mustard seeds