Soak the rice and urad dal for 4 to 6 hours. Into this add methi too.
Grind the rice and dal in mixer adding half cup water.
If needed add little more water. But remember batter should be thick and smooth.
Leave this overnight for fermentation.
After it gets fermented add salt and mix well.
To make mango puree:
Wash the mangoes, peel and make a puree.
If the mangoes are not very sweet add sugar as per your taste.
Add cardamom powder if you wish.
To make mango dosa:
Take a non-stick pan or tawa and heat it well.
Take enough batter and spread well.
Keep the flame on medium for 4 minutes.
Sprinkle 1 teaspoon of oil on top (optional).
Spread mango puree all over the dosa using a spatula.
Wait for another 5 minutes until the bottom part turns brown or the edges start losing the touch with the pan. By this time, the puree will lose its water and get dried.