- Halve eggs lengthwise and remove the yolk, reserving the whites. Add the yolks to a mixing bowl along with the mayonnaise, vinegar, mustard, and salt. Mix for a few minutes on medium speed until smooth. 
 
 
- Spoon half the yolk mixture into a pastry or food bag (or add to whites with a spoon) and fill 12 of the egg whites. 
 
 
- Add the truffle oil to the remaining yolk mixture and mix well. Fill the remaining 12 egg whites with the truffle yolk mixture.
 
 
- Garnish half of each with bacon and half with green onions. Keep refrigerated.