Beat the eggs with the flour, melted butter and a pinch of salt until smooth.
Heat a nonstick skillet lightly greased with butter. Pour in a ladleful of crepe mixture and cook until golden brown, then flip and cook the other side.
In a skillet, trifle the mushrooms with a drizzle of oil. Add the béchamel sauce, Fontina cheese and diced cooked ham. Stir well.
Stuff each crepe with the mushroom, cheese and ham mixture. Fold into a bundle.
Arrange the crepe bundles in a baking dish. Bake at 180°C (350°F) until au gratin.
Note
For an even more mouthwatering version, you can add a sprinkling of Parmesan cheese on top of the dumplings before gratin. This will add an irresistible crunch and more flavor.