Preheat oven to 200°C
Cut croissants in half horizontally. Spread mustard on one half of the croissant to taste.
Fill each croissant with ham and cheese.
Place filled croissants into an ovenproof dish.
Whisk eggs and cream together well. Season with salt and pepper.
Pour egg and cream mixture over the croissants and allow to stand for 5-10 minutes to allow the croissants to absorb the mixture.
Sprinkle with cheese and bake for 20 minutes. Reduce head to 180 and cook for a further 15-20 minutes. The egg mixture needs to be set and the top golden brown.