Combine all the ingredients listed under meatballs. Form 8 large golf sized meatballs from this mixture.
Heat up a non stick pan, add ½ cup water, star anise and the cinnamon stick to it. Slowly slide in the meatballs and bring this to a boil. Once the water starts boiling, reduce the flame slightly and let the meatballs cook in the liquid. Turn them around only once or twice. Once all the liquid has evaporated, toss the meatballs in the pan and let them glaze a nice golden brown in their own fat. Switch off the flame.
In another saucepan, start making the sauce. Add the butter and garlic. Saute for a minute and add the rest of the ingredients. Bring this to a quick boil, reduce the flame and let this simmer for 10 minutes till the sauce thickens enough to coat the back of a spoon. Toss the meatballs in 2-3 tablespoon of the sauce while still hot and set aside.
To make the onion rings, heat up oil in a deep vessel or kadhai. Season the tempura flour with salt and chili powder and slowly add water to it. Keep mixing till there are no lumps. The batter should be thick in consistency (same as pakoda batter) so that it coats the onion rings.
Once the oil is hot, dip each onion ring in the tempura batter till it's evenly coated and fry on high heat till golden brown. Remove with a slotted spoon and drain the oil on tissue paper.
To assemble the burgers, slice each burger bun in half and lightly heat on each side with a little butter. Top the bottom half with 4 meatballs, and add cheese to it. Place this on a hot pan, cover with a lid and heat it up for a minute till the cheese melts. Top this with onion rings, lettuce and more sauce. Serve with some chilled beer.