Whisk the eggs in a bowl, slowly add the flour and the milk to form a smooth and homogeneous cream. Use this batter to make the crespelle by pouring a ladleful in a large, non-stick pan and cooking it for a few minutes until golden. Repeat until the batter finishes. Place the ham and fontina PDO on the crespelle. Fold them and place them on a buttered baking tray. Cover with the béchamel and a few curls of butter. Add salt and pepper to taste and bake au gratin in the oven for 15 minutes at 180°.