Trim any excess fat from pork tenderloin, then slice it into 16 to 20 medallions
Flatten the pork slices with the heel of your hand or the side of a knife. Sprinkle lightly with kosher salt and freshly ground black pepper.
Trim the green onions, then cut each into 3 or 4 pieces.
Place a few pieces of green onion on a meat slice and roll up. Combine the garlic, soy sauce, honey, oil, hoisin sauce, and ginger in a shallow baking dish. Place the pork rolls in sauce mixture seam-side down and turn to coat. If preparing a few hours ahead, cover and refrigerate.
Bake, uncovered, for about 15 minutes or until meat is no longer pink in the center. The minimum safe temperature for pork is 145 F (USDA). During baking, baste the pork tenderloin rolls frequently with the sauce. Remove the pork to a plate and keep warm.
Pour the juices into a small saucepan. Combine the cornstarch with 1 tablespoon of cold water and mix until smooth. Stir into the juices.
Place the pan over medium heat and bring to a simmer. Cook until thickened, whisking frequently.