Rava Masala Dosas is my favorite! It requires no grinding, the batter once mixed can be used instantly and the chewy-crisp texture of the dosas is superb.
The most important factor in the making of rava dosa is adjusting the heat control and the consistency of batter. An iron tawa requires higher heat as compared to non-stick pan. I have used an iron tawa and so adjust heat according to the pan you use to prepare dosas. You need to be around the stove while preparing these dosas. And to get crispy dosas cook it on a slow flame.
Stir the batter well before spreading the dosas as the solids always settle at the bottom. The batter should be thin as rava soaks up lot of water while cooking. So try this and let me know your experiences 
Ingredients of Rava Masala Dosa
For Making Dosa
2 cups semolina/rava
1/2 cup rice flour
1/2 cup maida (all-purpose flour)
1 1/2 tsps cumin seeds
1 tsp grated ginger
curry leaves – few (optional)
finely chopped green chillies – 1 or 2
salt to taste
water – 6 cups (approx)
oil as required
For Potato Masala Filling
3 big potatos, boiled, peeled and chopped into small pieces
1 inch piece of fresh ginger, peeled and minced
3 green chillis slit lengthwise
2 big onions thinly sliced
¼ tsp turmeric pwd
salt
2 tbsp oil
1/4 cup water
For tempering/seasoning potato masala
1 tsp mustard seeds
1 tsp cumin seeds(jeera)
1 tsp urad dal
1 tsp chana dal(Bengal gram)
7 – 8 curry leaves
a pinch of asafetida powder
Method of Rava Masala Dosa
For making potato filling
1. Heat 2 tbsp of oil in a cooking vessel. Add the mustard seeds and let them splutter. Lower heat, add cumin seeds, urad dal, channa dal, curry leaves and fry till light brown, approx 10-15 seconds. The tempering should not burn.
2. Add curry leaves, asafetida powder, chopped green chillis and minced ginger. Mix and immediately add the sliced onions.
3. Fry till transparent, add turmeric and salt. Now add the chopped potato. Sprinkle 3 tbsp of water and let it cook with lid on medium heat for 3 minutes. Turn off heat and adjust salt.
For Making Dosa
1.Combine all the ingredients for dosa except oil and let the rava dosa batter sit for half an hour to an hour.
2. In a 8 – to 10 – inch nonstick griddle or frying pan heat a small amount of oil over medium heat until a light sprinkling of water sputters and crackles on surface of pan.
3. Before frying each dosa, stir batter well. It should be thinner than crepe batter, so it will spread easily on the griddle. It might have thicken after a while as rava absorbs the water. At the time of making dosas add more water such that it is of pouring consistency (like thick buttermilk).
4. Ladle about 1/3 cup batter onto the hot, griddle in a circular motion, starting from the outside and moving in, to make a thin pancake.
5. Fill the gap in the middle with dosa batter. Don’t drop batter like a thick lump but pour all over, evenly, filling the gaps. Pour 1-2 tsps of oil like drops along the edge of the dosa and the gaps in the middle.
6. Increase heat to medium flame and let the dosa cook for around 3 mts. At this point increase flame to high and let the dosa roast for a half a minute or so. If you want a slightly softer dosa, remove the dosa at this point.
7. If you want more crispier dosa than let it cook till it reaches a nice golden brown colour.
8. Add potato filling inside the dosa and roll. Serve hot with chutney and sambhar.