Wash the urad dal 4-5 times and then soak in water for 5-6 hours.
Grind it to make a thick paste with little amount of water.
Mix semolina, ginger chilli paste, curry leaves, cumin seeds and salt in it and cover it and keep it aside.
In the meantime make the potato masala for stuffing.
First of all mash the potatoes.
Heat a pan with oil in it and then add the cumin seeds in it.
When they crackle then add the chopped onion in it and when they become transluscent then add the ginger garlic chilli paste in it.
Cook it till the raw smell of garlic has gone and then add the spices, salt along with water.
Cook it for 2 minutes and then add mashed potatoes in it and then mix it well and again cook it for 5-6 minutes in low flame till the masala mix with the mashed potatoes.
Let the masala cool and then make small balls of it.
Make a layer of coating with batter.
Brush the apam pan with oil and put the vadas in it. Cook both the sides of the vadas till golden brown in colour.
Now your stuffed medu vadas are ready.
This is the time to make the chaat by placing 4-5 vadas in a plate and then put all the ingredients of the chaat one after another.
Now your stuffed medu vada chaat is ready to serve.