Add the flours and salt to a large mixing bowl, and make a well in the centre. Add the egg, and slowly whisk in the flour from the edges of the well. Add the water gradually, whisking constantly to ensure a lump-free mixture. It feels like a huge amount of water, but the mixture thickens up when it sits.
Leave the batter to rest for at least two hours, or overnight in the fridge.
When you’re ready to fry, preheat a large crepe or frying pan. It needs to be very hot for the crepe to get its signature lacy look.
Add a small pat of butter and evenly grease the pan. Pour in just enough batter that will coat the base of the pan thinly, and cook for 2-3 minutes on the first side, until crisp and golden brown. Flip and cook the other side for 1 minute to cook through, then keep the crepes warm in a low oven while you make the rest.
When you’re ready to assemble, fry your eggs in a separate pan and gather the cheese and ham. Put a crepe back in the original crepe pan crispy-side-down. Pop a few slices of ham and a small handful of cheese in the centre, topped with an egg, and then fold each quarter of the crepe towards the middle to contain the toppings in a square.
Serve with a grind of black pepper and pinch of salt.