To trigger the egg icon, hit the Ctrl key, the Shift key and the ~ key. On some keyboards in other countries, you have to click something other than the ~ key. I'm not sure what.
When you hit these 3 buttons, the console comes up. In the console window type: SetFlag and then hit the space bar. Within the quotation marks that will appear, type EGG and hit the enter key.
Now, there are a bunch of places you can use this "egg" icon for interesting results:
Go to the old ruins at Chateau de Blanchefort (top of mountain) and click on the sign pointing to Mt. Cardeau and select the egg icon.
While following Prince jame's men on Day 1, 6-10 PM, click on either man and select the egg icon.
Click on Jean at anytime and select the egg icon.
Grace will receive spam on Sidney.
Go to the Rennes-le-Baines (the tavern) and click on the barman. Totally fantastic!
Click on the chicken at any time and select the egg icon.
Click on Grace at anytime and select the egg icon.
During Day 2 10-12 PM, go to refrigerator in the hotel kitchen and click on the egg icon.
Click on Emilio during day 1, 10-12 PM while he is sitting in the lobby reading a newspaper, and select the egg icon.