Heat a spray of oil in a non-stick frying pan on a medium heat. Ladle in ¼ of the batter, and swirl the pan to make a thin crêpe covering the base of the pan. Crack the remaining eggs, one at a time, into a sieve to remove the excess white. When the sides of the pancake start to set, add an egg. Add a lid or baking sheet to the pan and leave for 2 minutes for the white to start to turn opaque. Add a spoonful of the spinach and a few pieces of ham. Leave to cook until the egg white is set but the yolk is still runny, and the galette is golden brown underneath.