Mix the beaten eggs with a pinch of salt, flour and milk until you have a smooth, lump-free cream. Pour the mixture into a non-stick pan and cook the crêpes. Fill with the béchamel sauce mixed with the mushrooms and close using a single chive. Pre-heat the oven to 180 °C and grill for 10 minutes. Use a hand blender to blend the cheese with the hot milk to obtain a creamy sauce. Serve by first drizzling the cheese sauce over the plate and then positioning the piping hot crêpe on top.