Cut tenderloin crosswise on diagonal to make long, 1/2-inch-thick slices; pound thin. Roll up 1 asparagus spear and 1 scallion in each beef strip. In large skillet, heat 2 tsp. sesame oil over high heat. Sear rolls on all sides, about 1 minute; transfer to plate. Add remaining ingredients to pan, whisking until thick, about 2 minutes. Slice rolls into 1-inch pieces. Serve with sauce.