Wrap the unpeeled sweet potatoes potatoes in wet paper towels and put them in the microwave for 10 minutes on 900 Watt.
While those are steaming, drain the chickpeas and mash them in the bowl. They can still be a bit chunky if you like. Thinly dice the red onion and put in the bowl as well.
When the sweet potatoes are cooked, take them out. Take the peel of, and cut the flesh in chunks and add the bowl. Add in the spices and give everything a good mix. Form 4 patties from the mixture.
Heat the oil in a pan and cook the burgers for about 5-7 minutes per side on medium heat. They will remain a bit soft on the inside.
While those are cooking, scoop the avocado and slice in thin slices.
Build the burger by putting on the burger, avocado, mayo, ketchup, pickled onion and rocket. Enjoy!