I know how to fix a split mayonnaise made with olive or vegetable oil - that's not a problem.
I have made Kenji Lopez-Alt's recipe for animal fat mayonnaise (bacon fat, for putting on a burger). It emulsified beautifully, chilled wonderfully.. and then as soon as you put it on a burger it gets too warm and splits faster than a gymnast at the Olympics.
The recipe I used:
2 egg yolks
1.5tbsp Dijon
1tbsp white wine vinegar
salt and pepper
600mL bacon fat
800mL vegetable oil
Two egg yolks should be more than enough to emulsify this, and indeed were -- I had to add tons of vegetable oil just to get the right consistency. But as soon as the bacon mayonnaise gets above fridge temp, it splits immediately. It re-emulsified with agitation, but that's a bit tough to do when one is trying to serve a burger in a restaurant. Help?