1. Using the egg topper, crack the narrow end of the egg shell. Carefully remove the top of the shell using a paring knife to help separate it.
2. Pour the egg out of the shell into a medium bowl. Place the empty egg shell into a separate bowl with two cups of water and the vinegar.
3. Submerge it in the vinegar solution, let sit for 30 seconds and then place upside down in an empty egg carton to dry.
4. Repeat with the second egg.
5. Whisk both eggs together and season with salt.
6. Heat the sabayon pot over medium heat and add the butter. Stir in the eggs and whisk constantly until small curds are developed and the eggs are the consistency of thick cream.
7. Remove from the heat and stir in the crème fraiche, ham or bacon, cheese, chives and season with black pepper.
8. Place two cleaned shells upright on two eggshell holders and spoon the eggs into the egg shells. Fill to the top.
9. Place one brioche "soldier" on top of each egg and two plouches of watercress alongside. Serve immediately.