Start off by pre-heating the oven to 200°C, pierce the potatoes 3/4 times each and place on a baking tray. Bake for 35 minutes until really soft.
Remove from the oven and leave to cool.
Heat the vegetable oil in a saucepan, add the onions, ginger paste and garlic paste together with the green chillies and cook for 2-3 minutes on a medium heat.
Add the red chilli powder, cumin powder, coriander powder, salt, turmeric and coarse black peppers to the pan together with the freshly chopped coriander and sweet corn kernels and cook for a further 1-2 minutes. Remove from the heat and leave to one side.
Once the potatoes have cooled, slit them in the middle and scoop out the pulp. Mash them and add the garlic butter along with the chopped onion and sweet corn and combine well.
Add half the polenta, combine well and shape the mixture into 10 burger/patty shapes, it will be quite soft (you may want to use some oil to moisten your hands which will help shape them), each burger should be about 7cm diameter.
Carefully dip each burger into the remaining polenta, dust off any excess.
Carefully place burgers on an oiled baking tray and refrigerate for about 30 minutes
When ready to cook, put them in the oven on a lightly oiled baking tray for 15 minutes. Tip: Alternatively pan fry the burgers for 2-3 minutes each side until browned (rotating a few times
Serve the sweet potato tikkis in the buns (toasted if you like) with a dollop of salsa and mayonnaise, a cheese slice, an onion ring and a tomato slice. Serve and enjoy.