Place the Sichuan chili flakes, chili powder, toasted sesame seeds, salt, sugar and MSG (if using) in a large heatproof bowl. Add the vinegar and 3 tbsp of canola oil. Mix until the chilies are evenly moistened.
Add canola oil to a medium pot. Add the onion, garlic, ginger, and green onions.
Cook over medium-low heat for approximately 15 minutes, stirring occasionally, until the edges of the aromatics begin to look dry and lightly golden. The aromatics should cook gently. If they begin browning too quickly, reduce the heat.
When the aromatics are lightly golden, add the star anise, bay leaves, cinnamon stick, and Sichuan peppercorns. Continue cooking for approximately 5 minutes.
Add the cilantro last. Continue cooking over low heat until the aromatics are golden, dry-looking, and fragrant. DO NOT allow them to become too dark or burnt, as this can make the oil taste bitter.
Carefully strain out all the aromatics and whole spices. Return the strained oil to the pot and heat it to approximately 200°C/395°F, then turn off the heat.
Carefully pour approximately one-third of the hot oil over the chili mixture. It should bubble immediately.
Stir thoroughly, then pour in the second third. Stir again before adding the remaining oil. Continue stirring until everything is evenly combined.
Let the chili oil cool completely before transferring it to clean, airtight jars.
Keep it refrigerated and always use a clean, dry spoon. For the best flavour and quality, enjoy it within about one month. The aroma and freshness will gradually fade over time.