In a small bowl, combine the milk, cream and eggs; beat with a rotary egg beater. Add the salt, pepper and onions.
Sprinkle half of the grated cheese in the bottom of the pastry shell. Arrange the fiddlehead tips over the cheese, then add the bacon, breaking it into bite-sized pieces.
Pour in the milk mixture, add the rest of the cheese, and grate fresh nutmeg over the top.
Bake at 375 degrees for 30 minutes, or until a knife inserted in the custard comes out clean.