In a large bowl, combine the rice, flour, semolina, plain flour. Add yogurt, salt, chillies, ginger, cumin, chopped onion, black pepper and curry leaves.
Pour in 2 cups of water first and mix well. Add another 2 cups of water and mix again. The batter should be very thin and watery.
You can use the batter immediately or let it rest for 30 min.
Heat a dosa pan with edges on the highest flame.
Stir the batter well before every dosa because the semolina settles at the bottom.
Once the pan is very hot, pour a ladle of batter from a slight height, moving around the pan. Then pour more so that the pan is covered. As the batter is thin, it will naturally form holes and gaps which is characteristic of rava dosa.
Cook for 1 min. Drizzle ghee generously over the dosa. Reduce the flame to medium-high and allow it to cook until the edges turn golden and crisp.
Loosen the edges, flip and cook the other side for about 30 sec. Flip once more, then fold and serve hot.
Keep the batter watery to create the characteristic lacy holes in the dosa.
After using up half of the butter, you might have to add 1/2 cup or more of water to make it thin again. (Batter might become slightly thicker as the semolina absorbs water)
Stir the batter before making every dosa as rice flour and semolina tend to settle at the bottom of the bowl.