Heat sesame oil in a pan on medium heat.
Add chicken to the pan and sauté until cooked through, 8-10 minutes.
Remove the chicken and place in the slow cooker. In the same pan, sauté onion until translucent, about 5 minutes.
Combine chicken and onion with rice, pepper, and vegetables. Scrape the pan and add the remaining sesame oil to the ingredients.
Heat on low for 1 hour or high for 30 minutes.
In the meantime, scramble the egg and toss it in just before serving. Sprinkle on the sesame seeds and green onion before serving.