Grease your kitchen table top or the back of 2 big plates with sufficient oil. Keep flat spatula ready before starting.
Sieve the besan , add turmeric powder and salt.
Make a paste of ginger, green chilli using and very little water.
Make thin and smooth buttermilk by whisking the yogurt and water together. Add the ginger-chilli paste and lemon juice to it.
Mix the besan, buttermilk together into a smooth batter making sure there are no lumps at all
In a non stick kadai heat 1 tsp oil on medium heat add the besan batter. Stir continuously preferably with a silicone spatula making sure the batter does not stick to the sides or the bottom of the pan.
At no point should one stop stirring or the mixture will form lumps. Keep cooking this mixture till it is quite thick and spreadable.
To check if your mixture is ready, spread a little batter on a greased thali and let it cool. If it rolls smoothly then it is done but if it sticks to your fingers, you need to cook it a little more.
Once ready, pour the mixture on a greased platform or thali, be quick in spreading it into a thin uniform layer.
Cut 1.5-2 inch strips and start rolling once it has cooled down. If the strip is too long, make 2 khandvis out of them. Continue doing the same until all the strips have been rolled neatly.
In a tadka pan or a small non stick pan, heat oil \; add mustard seeds. Once it starts to splutter, add the hing ; the curry leaves. Then add the chilli powder; immediately remove from fire ; pour the tadka on the rolled khandvis.
Sprinkle the chopped coriander ; the sesame seeds and serve hot. You can also garnish with some freshly grated coconut.