Pre-heat the oven to 180⁰C.
Using a rolling pin, roll out the slices of bread until they are completely flattened (roll from side to side to encourage a more square shape).
Butter both sides of the bread well.
Press the slices of bread into 6 holes of a muffin tin.
Gently fry the shallots in the oil until golden.
Put half the grated gruyere into the bread nests, top with caramelised shallots and then put the rest of the gruyere on top.
Season each nest well with freshly ground salt and pepper. (I find seasoning the egg mixture results in it sinking to the bottom of the bowl and staying there)!
Whisk together the eggs, milk and nutmeg and pour into the nests and then sprinkle with cayenne pepper.
Place in the centre of the oven and bake for 20 minutes or until cooked and golden.
Once cooked remove from muffin tray, allow to cool and put in the fridge until needed or enjoy hot with your favourite salads.