Croque Monsieur

I thought I'd try and make a 'proper' Croque Monsieur today. I'm at home, I'm too knackered to put my mind to anything even remotely involving abstract thought, so I thought today was the day. Also, I'm trying to take seriously the challenge laid down by my friend Hazel (wife of Brizey) in her excellent blog (The Grumbling Tummy) that in 2013 I will choose a different recipe book every single week and cook a recipe from that book that I have never attempted before.

So, last week it was Mejadra from Yotam Ottolenghi's Jerusalem and this week it's Croque Monsieur from the book M&S France: the food and the lifestyle (2005).

Here's my question: when you're frying the sandwich before you put it inder the grill - is there a way to keep the sandwich glued together? Mine kept collapsing.