Start by heating a large skillet over medium heat and adding a drizzle of oil. Once hot, add diced chicken and sauté for 5-7 minutes until fully cooked, stirring occasionally. Toss in the diced vegetables and cook for another 2-3 minutes until they soften. Finally, mix in the ketchup and cooked rice, stirring well to combine and heat through for about 2 more minutes, allowing the flavors to meld.

In a separate non-stick pan, melt a small pat of butter over medium-low heat. Crack the eggs into a bowl, whisking them until combined with the parmesan cheese. Pour the egg mixture into the heated pan and gently swirl to cover the base. Cook for about 2-3 minutes, or until the edges are set but the center is still slightly runny; aim for a soft, custardy texture, avoiding browning.

Once the omelette is ready, spoon the chicken rice mixture onto the center of the omelette. Using a spatula, carefully fold the sides of the omelette over the rice mixture. You can either fold it over completely or let it rest on top for a less formal presentation. Let it cook for another minute, allowing the residual heat to finish the omelette without overcooking it.

To plate your Omurice, gently slide it onto a warm plate, letting the omelette drape over the rice filling beautifully. Drizzle additional ketchup or your choice of demi-glace sauce on top for an extra burst of flavor. Consider garnishing with finely chopped green onions or sesame seeds for a delightful finishing touch. Enjoy your comforting homemade creation!