Trim excess fat and silverskin from tenderloin. Cut into 1-inch pieces, pat with paper towels, rub with some sesame oil, and season with salt and freshly ground black pepper.
Place a medium skillet over medium high heat, add 1 tablespoon sesame oil. When oil shimmers, add pork and cook until browned and cooked partially, about 2 to 3 minutes per side.
Remove pork to a plate, return skillet to stove, and add garlic. When garlic is fragrant, add green beans and stir occasionally until browned, about 3 minutes. Add sherry and hoisin, stir to combine, and cook until beans are tender and sauce is reduced slightly and sherry smell is cooked off, about 4 minutes. Return pork to pot, turn to coat in sauce, season with salt and freshly ground black pepper. Sprinkle with sesame seeds and green onions, if using, and serve over rice.
Recipe courtesy of Aida Mollenkamp