This is a cheat's version of the classic French sauce, Aioli. It doesn't pretend to be the real thing, but it is very good for what it is: a garlic-flavoured mayonnaise. For authentic versions of aioli, see separate entry on aioli.
Put garlic and oil in blender, and blend until completely smooth.
Blend in 1/4 of the mayonnaise, then stir in the remaining mayonnaise.
Make this up to 8 hours ahead, and refrigerate until needed. Tastes best anyway if you let the flavours blend for a bit.If you need the sauce thinner, you can add a bit more olive oil.Tip: add a tablespoon or two of honey, and toss with shredded cabbage and a handful of raisins for a great coleslaw.Use up within 3 to 4 days, as the garlic can go off in the mayonnaise.