1.) First, make the béchamel sauce. In a saucepan, heat butter until foaming then add the flour. Cook until smelling biscuity (approx 1 minute), then add the milk a little bit at a time, whisking as you go. Turn the heat off and add nutmeg then the cheese and stir in until melted.
2.) In a large bowl add flour, milk then eggs and whisk thoroughly until the batter is smooth. Stir in butter. It should be the texture of single cream.
3.) Make your pancakes. Pile them up with alternating layers of béchamel and ham between the pancakes. Top with a layer of béchamel then grill until the top has blistered. Serve in slices.