8 ounces (1 cup) mung beans (whole moong daal)
¼ cup basmati rice
1 cup spinach leaves, stems removed
1 green chile, chopped
1 teaspoon kosher salt
Neutral oil (such as safflower), for cooking
Soak the mung beans and rice together in a bowl of cold water overnight.
The next morning, drain them and tip them into a blender. Add the spinach, chile, salt, and 1½ cups water. Blend until you have a paste.
Heat a frying pan and, once hot, tip in a ladle of the batter and spread it in a circle using the back of the ladle. Drizzle ½ tsp. oil on top and cook on medium heat for 2 minutes before turning the dosa. Cook another minute on the other side, then remove from the pan and keep warm while you cook the remaining batter.
Do ahead: The batter will keep in an airtight container in the fridge for 3–4 days.