Gently squeeze off juice from beetroot, add in potato, chilli powder and salt. Mix well.
Make round shape ball from above mixture. Flatten it up and put 2 tbsp mayonnaise in the middle. Seal and make round shape patty.
In a bowl, add corn flour, water and salt. Mix well until smooth mixture is formed.
Coat burger patty in above batter and then roll in breadcrumb from all sides. Place this burger patty in refrigerator for half an hour.
Heat oil in a pan (medium flame) and pan fry burger patty from both sides until light brown in colour.
Spread 1 tbsp vegan mayonnaise on each half of burger bun.
On bottom half of burger bun spread 1 tbsp caramelize onion and top it up with burger patty. Spread remaining caramelize onion and avocado mash on burger patty and top it up with lettuce leaves. Cover it up with other half of the bun and serve.