Whisk the eggs in a bowl. Mix in the cottage cheese. Add ground psyllium husk powder while stirring to incorporate it smoothly, without lumps. Let the mixture rest for 5 minutes until the batter has set.
Place a frying pan over medium heat. Add a generous amount of butter and fry the batter like small pancakes for a couple of minutes on each side, until they are golden. Make two pancakes per serving.
Assemble a sandwich with sliced ham and cheese between two of the warm pancakes. Add finely chopped onion on top.
Serve the Croque Monsieur warm with leafy greens.