In a large heatproof bowl (ceramic or metal, not thin glass), stir together the gochugaru, árbol flakes, Sichuan peppercorn, sesame seeds, sugar, salt, and MSG. Use a bowl with plenty of headroom, since the oil foams up when it hits the flakes. Set a fine-mesh strainer and a paper-towel-lined plate nearby.
Combine the oil and sliced garlic in a saucepan over medium-low heat. Bring to a gentle sizzle and cook, stirring often, until the garlic is pale gold, about 6 to 10 minutes. Scoop it out onto the paper towels; it crisps as it cools.
Add the shallot to the same oil and fry until golden brown, about 5 to 8 minutes. Scoop it out to join the garlic.
Add the ginger, star anise, cassia, and bay to the oil. Raise the heat to medium and let it all sizzle gently until very fragrant and the ginger looks dry and lightly browned, about 5 to 8 minutes. Fish out and discard the whole aromatics.
Bring the infused oil up to hot but not smoking, around 350°F. Carefully pour about a third of it over the chili mixture, stirring as it crackles and foams. Wait 30 seconds, then pour in the rest and stir well.
Stir in the fermented black beans, soy sauce, and sesame oil, then fold in the reserved fried garlic and shallot along with the peanuts. Taste carefully and adjust salt or sugar.
Let it cool completely, then transfer to a clean jar. It's ready right away, but better after a night in the fridge.