Preheat the oven to 425 degrees, butter an oven-proof baking dish and place on a baking sheet lined with parchment.
Cut cauliflower and broccoli into medium size florets and boil for no more that 10 minutes before plunging them in ice-cold water to stop the cooking and to refresh their colour. Then drain and pat dry.
Meanwhile fry bacon till browned but not crisp and drain. Arrange the veggies in the buttered dish topped with a scattering of bacon.
In a separate bowl, add the flour, slowly beating in the eggs followed by cream and milk. Season with salt, pepper and nutmeg before mixing in two thirds of the cheese.
Pour the mixture evenly over the vegetables, sprinkle the remaining cheese on top and bake for about 25 minutes till bubbly and golden (keep under a broiler for a few minutes if the top needs more browning).
Insert a skewer and if it comes out clean, it's done.
Adapted from Around My French Table by Dorie Greenspan