Method

Start by lightly frying the pancetta lardons until golden, spoon onto a plate lined with a sheet of kitchen roll and place to one side.
Crack the eggs into a large mixing bowl and whisk together with the milk, a few sprinkles of of black pepper, grated whole nutmeg and most of the grated Comté and cheddar. Add most of the pancetta, all of the bread cubes and the tomatoes. Mix everything together, cover the bowl and place in the fridge for at least 30 minutes.
Meanwhile, slice the mushrooms and season with a little salt. Place a large frying pan on a medium heat and add 1 tablespoon of olive oil. Add the mushrooms and fry until golden, then spoon into a bowl and place to one side.
When the mixture has sat for a while, pre-heat the oven to 190c/170c (fan), take a large 30-35 cm round, shallow casserole dish and line with a piece of greaseproof paper. Mix the mushrooms into the bowl of soaked bread and spoon the mixture into the casserole dish, then sprinkle over the remaining lardons, grated Comté and Cheddar, Parmesan, dots of onion chutney and rosemary. Cover with a piece of greased foil and place in the oven for around 25-30 minutes.
After that time, remove the foil and place the pan back in the oven for 5 minutes, to crisp up and turn golden brown.
Once baked, allow to sit for 10 minutes, then slice into wedges and serve.