In a food processor or blender, combine the egg, mustard, garlic, lemon juice, hot sauce and salt and process until smooth. With the machine running and in a steady stream, add the vegetable and olive oil and process until emulsified.
Pour into a decorative bowl and fold in the green onions. Adjust the seasoning to taste. Cover and refrigerate for 1 hour before serving. (The sauce will keep, covered and refrigerated, for up to 24 hours.)
Yield: about 1 1/4 cups
*RAW EGG WARNING
The American Egg Board states: "There have been warnings against consuming raw or lightly cooked eggs on the grounds that the egg may be contaminated with Salmonella, a bacteria responsible for a type of foodborne illness. Healthy people need to remember that there is a very small risk and treat eggs and other raw animal foods accordingly. Use only properly refrigerated, clean, sound-shelled, fresh, grade AA or A eggs. Avoid mixing yolks and whites with the shell."