In a large mixing bowl toss the chicken tenderloins with the cornstarch.

Heat up the oil in a large skillet over medium high heat.

Brown the chicken quickly in the pan. Do not worry if the chicken is not cooked through, it will be cooking more later.

Remove the chicken from the pan.

In another skillet or the same one cleaned out add the sesame oil, onion and jalapenos.

Saute these over medium heat until they start to become tender and slightly browned

To the pan add the soy sauce, vinegar, brown sugar, garlic and ketchup.

Whisk the sauce together.

Add the chicken to the sauce.

Cook everything over medium heat until the sauce becomes thick and coats the chicken.

Serve over rice or mashed potatoes.