Rinse 1 cup urad dal thoroughly in clean water.
Soak it in enough water for 4–5 hours or overnight.
Drain the water completely before grinding.
Transfer soaked dal to a blender or wet grinder.
Add green chilies, ginger, and a little water.
Grind to a thick, fluffy batter. Do not make it runny.
Transfer batter to a bowl.
Mix in chopped onions (optional), curry leaves, coriander, cumin seeds, pepper, coconut, rice flour, and salt.
Whisk vigorously in one direction to incorporate air and make the batter light.
Wet your hands with water.
Take a portion of the batter, shape the vada batter into a ball, and make a hole in the center with your thumb.
Place it on a wet cloth or greased plate.
Heat oil in a deep pan on medium heat to fry vadas.
Gently slide vadas into the hot oil.
Fry in batches until golden and crispy, flipping occasionally.
Remove and drain on paper towels.
Serve hot Medu Vadas with south Indian coconut chutney and sambar.
Enjoy with filter coffee for a traditional experience.