For the ham and cheese croissants, salt the flour, crumble with fat and mix with curd cheese to form a dough. Let the mixture rest in the refrigerator for about 2 hours.
For the filling, chop ham, mushrooms and onion and fry in a little butter until the liquid has evaporated. Then let the filling cool down and mix it with the rest of the ingredients.
Roll out the dough to a thickness of about 5 mm and cut into triangles of about 15 cm. Place the filling on the dough and roll it up.
Form into croissants on a greased baking tray and brush with a little more butter. Bake the ham and cheese croissants at medium heat for about 25 minutes.