Wash the brown rice, urad dal and methi seeds for a couple of times under running tap water. Soak all the ingredients together in water for atleast 5 hours.
After 5 hours, drain the water and grind the batter in 2 batches. Use little water to grind the batter, as required.
Mix the batter well with your hands for a couple of minutes. Cover it with a lid, keep it aside in a warm place for fermentation. The process would take anywhere between 6 to 10 hours. Note - My batter fermented in 8 hours.
Once the batter is fermented, add salt to taste, mix lightly. Check consistency of the batter and add additional water if required to adjust consistency.
Heat a griddle, season it with some oil and then pour a ladle of the batter on to the hot pan.
Make thin crispy dosas by rotating the ladle with the batter clockwise on the hot pan. Pour oil on all the sides, allow the dosa to cook on low heat.
Flip or turn the dosas once they have cooked, add more oil and cook the other side.
Crisp Brown Rice dosas are ready to eat with sambar and chutney.
Note - If you don't plan to make dosas immediately after fermentation, add the salt, adjust consistency of the batter and then store it in the refrigerator until further use. Always cover the batter with a tight lid or store in a container.