Slice open the croissants and coarsely grate the cheeses.
Spread the outside of the croissant with the butter and layer in the cheese, followed by the ham and finishing with the cheese again.
Place under the grill until the cheese is oozy and melted and bubbling. If the croissant is cooking too fast at any point, cover the top with tin foil.
Whilst you are waiting for this, fry up your eggs in a drizzle of veg oil on a hot heat. Top the oozy croissants with the eggs when they are ready.
