Chop the onion, mushrooms, and garlic finely.

Heat a pan and sauté the chopped onion, mushrooms, and garlic until fragrant.

Add the cooked rice to the pan and stir well to combine with the sautéed ingredients.

In a bowl, whisk together eggs and 50 ml milk until smooth.

Pour the egg mixture into a heated pan and cook until partially set, then place the rice mixture on top.

Fold the omelette over the rice and transfer to a plate.

Prepare the sauce by mixing 150 ml milk, rice water, and tonkatsu sauce in a pan. Heat until slightly thickened.