Season both sides of the steak with the salt and pepper.
Add 1 tablespoon of the butter to a large saute pan on medium-high heat.
Add the steak to the hot pan and cook for 3 minutes or until nicely seared.
Flip the steak and cook for another 3 minutes.
Cut the steak into bite-sized pieces, then continue cooking on medium high heat.
Add ¼ cup of the teriyaki sauce to the steak. Simmer for 1 to 2 minutes or until steak reaches desired doneness.
Remove the steak from the pan and scramble the egg in the same pan, if using.
Add the carrot, shallot, and garlic to the pan and saute until fragrant.
Add the cooked rice to the pan and toss with the vegetables.
Add the mirin to the rice and stir to combine.
Add the chicken bouillon, the remaining tablespoon of butter, and the remaining ¼ cup of teriyaki sauce to the rice. Saute on medium heat, stirring to combine.
Top the rice with steak and sliced green onion. Serve with yum yum and ginger sauces, if using.