Roast the capsicum on direct flame till lightly charred. Dip it in a bowl of water and peel off the charred skin. Remove the seeds and chop roughly. Grind the corn with milk to a coarse paste.
Heat oil in a deep pan. Add onion and sauté till lightly browned. Add the ground sweet corn and one cup of water. Stir and cook.
Add the capsicum and stir. Add salt, fresh red chillies and simmer. Mix cornflour in quarter cup of water and add to the soup and stir. Cook till the soup thickens slightly.
Serve piping hot.