Hi! I tried the Croque Monsieur in smaller quantities - using 4 slices bread, 4 eggs and 60 ml milk. I baked it at 400F for 25 minutes and it looked well cooked and beautiful on the outside. However when cut, it was raw inside and wet. I did not leave it in the fridge overnight, only placed it in fridge for 15 minutes while the oven preheated. Help?
Nigella's Croque Monsieur Bake (from Nigella Express and on the Nigella website) is a type of strata, or savoury bread and butter pudding, where the mustard and ham sandwiches are soaked in an egg custard before baking. Nigella suggests assembling the bake the night before and letting the dish stand in the fridge overnight.
Our suspicion is that the dish did not stand for long enough before baking. The standing time is important as the bread will soak up the eggy liquid and when cooked the whole dish will set more easily. If the bread has not had time to absorb all of the egg then it is likely that some excess liquid will be left in the centre and so will not cooked quite as thoroughly. Try to let the dish soak in the fridge for at least 2 hours, and you may find it helpful to turn the sandwiches over in the egg mixture a couple of times to encourage the bread to absorb as much of the egg as possible.