No need to preheat the oven yet, this needs to soak overnight. Slice your Panettone into cubes which are around 1 inch square. Spray an 8x8 inch square pan with cooking spray and place the cubes of Panettone into the prepared pan.
Place the eggs, milk and spices into a large jug and whisk until there are no lumps of egg. Pour slowly over all of the Panettone cubes, then cover loosely with cling film and leave overnight, or for at least 8 hours
After 8 hours, preheat the oven to 180C/350F and sprinkle the light brown sugar over the top of the Panettone mixture. Place in the oven for 25-30 minutes, until golden and the middle is just set. If you give the pan a little shake, the whole thing should wobble as a whole and it should not be runny.
Leave to cool for 20-30 minutes, before serving warm with maple syrup.
Panettone French Toast Bake will keep covered, in the fridge, for 4 days. Best served warm. To reheat, place a slice in the microwave and heat for 30 seconds - 1 minute.