Mix together the teriyaki sauce ingredients in a medium saucepan. Bring to a simmer and cook until the mixture has thickened. Let cool. If you want to use it right away, only use 1/2 of the water that the recipe calls for, and then add 1 cup of ice after it comes off the heat to help it cool down faster.

Slice the tenderloin into round medallions.

Add half of the teriyaki sauce to a large gallon baggie with the pork tenderloin. Refrigerate and let marinate at least 4 hours, but it would be better to let it go overnight. Reserve the rest of the teriyaki sauce in the fridge.

Preheat your griddle over medium heat. Remove the meat from the marinade. Add the oil to the griddle. Add the pork tenderloin. Let cook for 3-4 minutes per side before flipping. The internal temperature should be about 135°F before you remove it. Don't overcook it! Pork gets dry when it is overcooked.

Slice, garnish with sesame seeds and green onion, and serve over steamed rice.