Cut each croissant in half lengthways and spread the bottom with dijon mustard. Layer cheese and ham and place the top layer of croissant on top.
Place a layer of three croissants in a greased baking tray and top with more cheese and ham, then add the final three with another layer of cheese on top.
In a sauce pan heat the butter until its foaming and stir in the flour. Cook for a minute or so until it smells biscuity, then gradually stir in the butter to make a smooth sauce. Stir in the salt and cheese and pour directly over the croissants and bake for around 30 minutes, until bubbling and golden on top.
Serve straight away, wear a beret.
Recipe by Cooking TV Recipes at https://cookingtv-channel.com/croque-monsieur-croissant-lasagna/