In a small bowl, mix together the vinegar, salt, MSG, Japanese mustard powder, and dashi.
Add the egg yolks to the food processor and then add the vinegar mixture.
Turn on the food processor and blend until all the egg yolks and vinegar mixture is incorporated.
While the food processor is on, slowly drizzle the canola oil into the food processor. Do not dump the entire container of oil into the food processor or it will not emulsify. Continue to add the oil until it’s gone.
Taste the mayonnaise to see if it needs more seasoning and adjust.
Serve immediately or put in an airtight container. This should last in the fridge for up to one week.