Place tenderloin in freezer for 10 minutes so you can thinly slice. You want to slice it about ⅛ inch thickness if possible.
Toss the pork in a bowl with the cornstarch, making sure everything is coated. Add oil to a large skillet over medium-high heat.
Shake off any excess cornstarch from the pork and cook for 4-5 minutes, or until the pork is charred. When it is done, remove from the skillet.
Add the garlic and ginger to the skillet, cooking for 30 seconds. Add the soy sauce, water and dark brown sugar and let it come to a boil. Add the pork back in and cook for 30 seconds. Add the green onions and serve over some rice.
Notes
Place pork in the freezer for 10-30 minutes so it is easier to slice thinly.
Be consistent with the size you slice the pork so it cooks evenly.
Cook the pork in batches so you don’t overload the skillet or wok and cool it down. You want to cook the pork quickly and adding too much at a time will slow the cooking process.
While not traditional, if you like some heat, add crushed red pepper flakes ¼ teaspoon at a time.