To make the dosa batter, wash the dal and rice thoroughly, then drain and soak in 900 milliliters of fresh water with the fenugreek seeds, covered, for 6-12 hours or until the grains have swelled and softened.
Tip the mixture into a blender and whiz until smooth, then transfer to a non-metallic bowl. Cover and set aside overnight, or until the mixture is frothy, light and full of volume.
Once the batter has fermented and you’re ready to get started, preheat the oven to 180°C/350°F/gas 4.
To make the filling, peel and roughly slice the onions, scrub and roughly chop the potatoes, peel and chop the plantain and squash. Peel the ginger and finely slice. Finely slice the chillies into rounds.
Place a large baking tray directly on the hob over a medium heat. Add one tablespoon of coconut oil, the mustard seeds, fenugreek seeds and curry leaves, and cook for two minutes or until sizzling. Add the onions, chilli and ginger, stirring to coat in the spices.
Add the potatoes, squash and plantain, followed by the tumeric. Give it a good stir and place in the hot oven for one hour or until the vegetables are golden and soft. Once cooked, smash it all up ready for filling your dosa.
Meanwhile, prepare your chutneys and pickle. For the tomato chutney, halve the tomatoes, then coarsely grate into a bowl, discarding the skins. Peel the onion and ginger and finely grate into bowl with the chilli. Squeeze in the lime juice and season to taste with sea salt and black pepper.
For the coconut chutney, crack open the coconut and scrape out the flesh with a fork (or coarsely grate) into a bowl. Finely grate in the lime zest and squeeze in all the juice. Peel and finely grate in the onion and ginger, then season to taste.
For the lemon pickle, quarter the lemon, discard the seeds, and finely chop. FInely chop the chilli (seeds and all). Place a small frying pan on medium heat with one tablespoon of vegetable oil. Add the cumin and mustard seeds, wait for them to pop, then go in with the curry leaves, lemon and chilli. Cook for 30 seconds, stirring constantly, then season to taste and pop into a little serving bowl. Leave to cool.
To cook your dosa, one at a time, place a large non-stick frying pan on a medium heat and grease with a little vegetable oil. Season your batter with sea salt and give it a good whisk. Add a ladleful of batter to the pan, using the back of the ladle to swirl it around getting it as thin as possible. Cook for five minutes or until the underside is golden and crisp. Drizzle a teaspoon of vegetable oil over the surface of the dosa (no need to flip it) and cook for one to two minutes more.
Load up your dosa with the spicy veggie filling, roll it up like a cigar and keep warm in the oven while you cook up the rest of the dosa. Repeat with the remaining batter.
Garnish the dosas with a sprig of coriander and serve with the chutneys for dipping. Delicious!