To prepare the chili mixture: In a large heatproof bowl, combine the red chili flakes, paprika, salt, five-spice powder, and sesame seeds. Mix well.
To infuse the oil: In a small pot over medium heat, add the cooking oil, ginger, scallions, and garlic. Cook for about 2 minutes, until aromatic. Remove all the ginger, scallions, and garlic from the oil.
To heat the oil: Continue heating the infused oil until it reaches about 325°F (163°C).
To make the chili oil: Carefully pour one ladleful of hot oil over the chili mixture and whisk immediately. Slowly pour in the remaining hot oil while continuing to whisk until evenly combined.
To finish: Carefully add the Chinkiang vinegar and stir to combine. Allow the chili oil to cool completely.
To store: Transfer the cooled chili oil to a clean, airtight container and refrigerate. For best quality, use within 2–3 months and always use a clean, dry spoon.