Remove any silver skin or fat from the pork tenderloin with a knife or by pulling it off carefully.
In a bowl, combine honey, soy sauce, brown sugar, garlic, rice vinegar, and toasted sesame seeds, if desired. Pour half of the marinade into a large Ziploc bag or a baking dish. Add the pork tenderloin and toss to coat. Set the remaining marinade aside.
Set the electric smoker or pellet grill to 225 degrees Fahrenheit. Close the grates to the open fire or heat element so the tenderloin does not cook too quickly.
Brush oil on the smoker grates to prevent sticking. Place the pork tenderloin on the grates and close the lid. Cook for approximately 1 to 1 ½ hours, until the pork has reached at least 145℉.
While it cooks, add the remaining marinade to a saucepan and bring to a boil. Mix cornstarch and water in a bowl, then add to the marinade once it's boiling. Continue whisking as it thickens, then remove from the heat.
If you like more caramelization: brush the pork with more honey garlic sauce, and open the grates so that the heat element/flame is exposed to the meat for the last 10-20 minutes of cooking time.
Slice into 2" pieces on a cutting board. Serve with additional sauce over top.