The amount of batter- moringa leaves proportion is entirely upto you. You can add as much or as less based on your preference. To me, half the amount of batter in leaves makes for a well balanced ratio. The amount of onion is also your own choice. While its optional, I personally would recommend it.
Mix the leaves along with the batter
until well combined. You can add some water (few tbsp or so) to thin down the batter if you want to make it thinner. It would give it a more lace kind of texture. But if you are looking for soft, medium thick dosas, you can skip the water.
Heat a skillet (cast iron preferable) and once hot ( drops of water should sizzle), lower the heat. Dropping the batter when the pan is hot will make it lumpy and you won't be able to spread it easily. Use a paper towel to grease the surface slightly. I use sesame oil since its a traditional choice but any oil should do. Make sure you wipe the excess since it would make the batter form lumps when trying to make dosas.
Drop a small ladleful of batter in the center and immediately spread it in a circular motion. The thickness depends again on your choice. You can make it as thin or thick. I wanted to make a slightly spongy dosa hence made it little thick. Add in the chopped onions quickly as well since once the batter starts to cook the onions wont stick to the surface. Increase the heat to medium.
Close it with a lid. This helps the top also to steam well while the underside is cooking.
Now the top is also cooked along with bottom part as you can see the brown spots.
Turn the dosa on the other side and drizzle some oil around the dosa. Cook for few more seconds. Repeat for all the dosas. Just make sure to decrease heat before adding in the batter and increasing it once the batter has been spread. If the skillet has become very hot, you need to sprinkle some water to cool it down a bit and then proceed with the rest of the dosas.