To build the sandwiches, slice open croissants, place a slice of cheese on the bottom, followed by the fried egg, then 2 slices of bacon and finish with another slice of gruyere.
Place the top lid on the croissant. Repeat on the other 3 sandwiches.
In a bowl, mix together the eggs and milk to make an egg batter.
Press down on each sandwich to flatten.
Heat a non-stick pan over medium heat and add the butter.
Dip the sandwiches into the egg batter and coat well.
Slide the sandwiches into the pan.
Cook until golden brown and then flip to brown the other side of the sandwich.
Remove the sandwiches from the pan and serve with a green salad.