In a medium bowl, combine the hoisin sauce, soy sauce, rice wine vinegar, minced garlic, and thinly sliced green onions. Whisk everything together until well combined. I like to add a pinch of salt to the sauce to give it more flavor. Place the pork tenderloins into the marinade, ensuring they are fully coated. Cover the bowl or transfer to a large sealable bag and refrigerate for at least 2 hours, or preferably overnight, to allow the flavors to penetrate the meat.

Preheat your oven to 425°F (220°C). Lightly spray a rack set over a baking sheet with cooking spray. Remove the pork tenderloins from the marinade, allowing any excess marinade to drip off, and place them on the prepared rack. Reserve the remaining marinade for the sauce. Roast in the preheated oven until the internal temperature of the pork reaches 138°F (59°C) when measured with a meat thermometer, which typically takes about 20-25 minutes depending on thickness. Remove the pork from the oven and transfer it to a cutting board.

While the pork rests on the cutting board, it will continue to cook, reaching a final internal temperature of 145°F (63°C), ensuring a juicy and tender result. In a small saucepan, bring the reserved marinade to a boil over medium-high heat. Reduce the heat and simmer vigorously, stirring occasionally, until the sauce has reduced to about 2/3 cup and thickened slightly, which should take approximately 3-5 minutes. This step is crucial for both thickening and ensuring food safety by cooking out any raw pork juices.

Once the pork has rested (about 5-10 minutes), slice it into 1/4-inch thick medallions. Arrange the sliced pork on a serving platter. Drizzle the warm, reduced hoisin sauce generously over the pork. Finish by sprinkling the toasted sesame seeds over the top for a beautiful presentation and a delightful nutty crunch. For a more authentic flavor, I like to toast sesame seeds myself in a dry pan until fragrant.