In a small saucepan, gently submerge the eggs in cold water. Bring to a boil over high heat, then reduce to medium heat and simmer gently for 4 minutes. Drain and cool the eggs under cold running water until they reach room temperature.
Heat oil in a non-stick frying pan. Cook bacon until crisp, about 2-3 minutes. Transfer to a plate lined with paper towel to cool slightly, then finely chop.
Peel the eggs, place in a bowl, then lightly mash with a fork. Mix in mayonnaise and bacon until fully combined.
Spoon the delicious egg mixture into the crispy vol-au-vent cases and arrange them elegantly on a platter.