Heat a large skillet over medium heat and add 1 tablespoon of butter or oil. Once melted, add diced chicken and sauté for 5-7 minutes until golden brown and fully cooked. Season with salt and pepper, then transfer the chicken to a plate and set aside.

In the same skillet, add another tablespoon of butter or oil. Toss in finely chopped onions and sauté for about 3 minutes until they become translucent. Stir in peas and carrots, cooking for an additional 2 minutes until tender.

Add day-old rice to the skillet, breaking clumps apart. Toast the rice lightly for 2-3 minutes, then drizzle in the ketchup. Mix thoroughly and cook for 2 more minutes.

Turn off the heat and scoop the rice mixture onto plates, forming oval mounds.

In a bowl, whisk together eggs and a splash of milk until frothy. Heat a nonstick skillet over medium-low heat and add 1 tablespoon of butter. Pour half of the egg mixture into the skillet and cook for 3-4 minutes until set but slightly runny in the center.

Carefully lift the omelet and slide it over one mound of rice. Allow it to drape over the rice gently.

Repeat the process with the remaining egg mixture to create a second omelet over the second rice mound.

Drizzle ketchup artistically over the tops of your Omurice before serving while warm.