These beef rice burgers are inspired by a Japanese fast-food chain MOS Burger. Some of their classic burgers use rice as the buns instead of bread.
When making the rice buns, I would recommend you to use short-grain white rice (sushi rice), as they are starchy and stickier, making it easier to compress them into buns (similar to making onigiri). If you want to make this vegan, you can also substitute the meat with oyster mushrooms or tofu.