Preheat the grill. In a small saucepan, on low-medium heat, melt down the butter.
Add the flour and mix into a paste. Whisk continuously on a medium heat for 2-3 minutes to cook out the taste of the flour. You do not want the mix to turn brown as this will change the flavour.
Add the milk 2 tablespoons at a time, whisking together into a silky paste before adding more milk. Repeat this until all the milk has been added. If you add the milk too quickly you will end up with a lumpy sauce.
Bring this mixture to a boil, add salt and pepper to taste and immediately reduce the heat and cook for a further 3 minutes before setting aside for later.
Cut your bread roll in half, add 2 tablespoons of your Béchamel (White Sauce) to the bottom half of the bread followed by your ham, salami, half of your spring onions and half of your cheese.
Replace the top half of the roll and place into a toasted sandwich machine. This will flatten your sandwich whilst browning the bread and adding some crunch. A preheated oven (200°C) will do a similar job.
When the sandwich is desirably toasted (+- 4 minutes) move it to a baking tray.
Pour the remaining Béchamel, then add mozzarella, spring onions and lastly chilli flakes over the top of the sandwich.
Place into the middle of the oven (so that it does not burn the cheese) and allow to grill for 5-10 minutes, removing when the cheese is starting to brown and bubble.
Whilst the sandwich is grilling fry your egg sunny side up or to your taste and set aside.
Remove from the oven, place the egg on top of the sandwich and season with salt, pepper and your choice of chimichurri or fresh basil.