Start by cooking the sushi rice using the instructions on the pack, or use my recipe for unicorn rice.
Once the rice is done cooking put it in a bowl and let it cool before using.
While the rice is cooking start by prepping the filling.
Bring a pan to medium/low heat and sauté the chopped onion until it turns translucent, add the minced garlic and cook for another minute before adding the beans.
With the back of the spatula stir while breaking the beans.
Add the spices, salt and pepper and cook for a few more minutes before adding the peanut butter and giving it a good mix. Now let it cool.
To form the rice balls you can use a onigiri mold or simple do it by hand. If you're using the onigiri mold you could rub some (toasted sesame) oil on the inside, so it's easy to remove the rice ball. Add some rice and create a little well, to this add a bit of the filling, top with rice and squeeze down to close. There should not be any filling coming out.
To make it by hand simply take some rice (wet or oil your hand a bit so the rice won't stick) make a well and add the filling. Mold it into your preferred shape to close.