Start cooking your rice and return to the kitchen 10-15 minutes before it's done.
Cut the chicken into pieces 2 cm wide and long, removing any fat in the process.
Peel and finely mince the onion.
Make the chicken rice
Heat up 1 tbsp (15g) of butter over medium-high heat.
Once it's fully melted, add the onion and sauté until translucent.
Add the chicken to the pan, season with the salt (0.5 tsp) and pepper.
Fry until the chicken is no longer pink, flipping it regularly.
Reduce the heat to medium, then add the ketchup and Worcestershire sauce.
Stir to mix well and fry for another 2-3 minutes to reduce moisture.
Add the cooked rice and break up the clumps.
Add the peas.
Mix well and divide the chicken rice into however many servings you are making.
Turn the heat to very low to keep it warm.
Make the omelet(s)
You need to make and stuff the omelets one at a time. If desired, turn your oven to low heat to keep the first serving(s) of omurice warm as you're making the rest.
Crack two eggs in a bowl and add 0.25 tsp of salt.
Beat thoroughly to break the egg whites.
Heat up 1 tbsp of butter in a pan over medium heat.
Once it's hot and starts to bubble (but not brown), pour in the beaten egg.
Tilt the pan to distribute the egg evenly and fry it until still slightly runny. Turn the heat off so it doesn't cook fully.
Assemble
Transfer one serving of chicken rice from the other pan onto the omelet.
Mold it into a small mound that runs along the middle from one side of the pan to the other, at a 90-degree angle to the handle.
Slide it away from the handle by tilting the pan.
Carefully fold the sides of the omelet over it. The lower side should be folded up naturally by the side of the pan.
Flip the omelet on a plate in a quick, but smooth motion.
It should be the shape of a rugby ball. If it isn't, mold it with your spatula or hands, but don't burn yourself.
If desired, put it in the pre-heated oven while you make the other omelets.
Drizzle some ketchup on top of the omelet(s) in a zigzag motion and keep the bottle handy at the table. Enjoy!