Mince and mash garlic to a paste with a pinch of salt using a large heavy knife.
Whisk together yolk, lemon juice, and mustard in a bowl.
Combine oils and add slowly to yolk mixture, whisking constantly, until all oil is incorporated and mixture is emulsified. (If mixture separates, stop adding oil and continue whisking until mixture comes together, then resume adding oil.)
Whisk in garlic paste and kalamata olives. Season with more salt, if needed (remember the kalamata olives are pretty salty-tasting. Add fresh ground black pepper, if desired).
Chill, covered, until ready to use. May be stored in the refrigerator as long as the use-by date on the carton from the egg yolk you used.
Serve with homemade fries, pretzels or pretzel chips, burgers, chicken, or steamed artichokes.