Mix the mirin, ketchup, oyster sauce, soy sauce and white sugar until they are dissolved.

Dice the mushroom, bacon, onion, carrots and scallion, and then put them into separate bowls for later use.

In a large skillet over medium heat, heat the oil together with onion, mushroom and carrot. With constant stirring, cook the onion until it is translucent. Then, add the bacon and cook it until the edge is a little brown.

Add the butter, followed by rice, spread and break the rice with a spatula. Keep folding the rice and cook it until most of the white steam (moisture from water) is gone, avoid burning of the rice.

Beat the eggs with milk until yolks and whites are completely blended. Season with salt and pepper to taste.

In a medium non-stick pan, heat the oil over medium heat, pour half of the egg mixture into the heated pan. Wait until the egg coagulate and form a uniform base.

Using a pair of chopsticks, grab one edge of the egg using one chopstick and the opposite side of edge with another chopstick, bringing the coagulate towards the center.

Holding the chopstick, start turning it anti-clockwise, while using your another hand to turn the pan in clockwise direction. The runny egg will start to form a spiral coagulate as you turn. Make more turns until the egg look nicely as a tornado.

Transfer the omelette while it is still slightly runny onto the prepared fried rice.

Repeat the steps for the remaining half portion of egg mixture.

Top the omelette rice with a pinch of chopped scallion and enjoy.