While the meat is cooking, cut your onion into slices.
Measure out ¾ cup of rice and place into two bowls.
You can make more than one serving at a time but its easiest to do one because you are going to pour the contents of the pan right over your bowl of rice, so you won't have to mess with dividing it if you cook one at a time.
Heat the oil over medium high heat in a small skillet. Add half of the onions and cook for 3-5 minutes, stirring occasionally until they have browned. (If you're doing both servings at once, use all of the onions.)
While the onions are cooking, measure out the the chicken stock, soy sauce, rice vinegar, and sugar in a bowl. Mix to combine.
In the bowl with the ½ of an egg, crack another egg and scramble.
Once the onion has browned, pour in half of the sauce and bring to a light boil. (If you're doing both servings at once, pour in all of the sauce.)
Cut the chicken into thin slices and place one cutlet into the pan over the sauce. Pour half of the eggs around the chicken and cover with a lid. (If you're doing both servings at once, pour in all of the eggs and use both chicken cutlets.)
Cook for 1-2 minutes or until the egg has set.
Pour the contents of the pan over the rice and top with green onions. (Divide the ingredients of the pan over both rice bowls if you make it all at once)