Peel the sweet potatoes and slice them thinly.
Boil them in water until soft.
Mash the boiled sweet potatoes and season with salt and pepper.
Spread oil in a pan and flatten the mashed sweet potatoes like a dough.
Slice the yuja thinly and place on top.
Evenly sprinkle mozzarella cheese over the sweet potatoes.
Cover with a lid and cook on low heat until the cheese melts.
Cut the finished pizza into pieces for serving.