The trick in making the crispy Rava dosa is the batter should be very thin in consistency. The Rava Dosa should not be prepared like the regular dosa by forming a circle with the ladle. You have to pour the batter with a ladle on the hot tawa from outside to inside. The batter might thicken as time passes in the process of making dosas. Keep 1/4 cup water handy and add to the batter to bring it back to the thin buttermilk consistency. Each time you pour the dosa, give the batter a stir as the flour mixture will tend to settle in the bottom. The batter should of pouring consistency like a thick buttermilk consistency but not very thick.