For the crepes: In a bowl, whisk together both flours and salt followed by the egg, milk and cider, making sure there are no lumps. Add the water: you may need more or less depending on how much the flour will absorb. Cover and let rest 2 hours to overnight prior using (does not need to be in the refrigerator).
When ready, check the fluidity of the batter. You may need to add up to another cup of water so the galette isn’t too thick. It should be the consistency of a thin batter. Pre-heat oven to 400 F. Prepare a crêpe pan with non-stick spray, then wipe it so there’s no excess. When pan is hot pour a few ladles of the batter evenly and cook about 2 minutes. Add ¼ cup, each Gruyère and ham, followed by a cracked whole egg. Fold each side of the galette so it looks like a square and cook an additional 2 minutes until it’s set. Place in the oven for 2 minutes to set the egg.
Finish the galette with greens tossed with olive oil, vinegar, salt and pepper. Enjoy with a glass of Sparkling Apple Cider from Brittany.