1. Cut croissants in half lengthwise, and cut each half into 4 to 5 pieces. Place croissant pieces in a lightly greased 10-inch deep-dish pie plate. Top with ham and cheese.
2. Whisk together eggs, next 5 ingredients, and, if desired, nutmeg in a large bowl.
3. Pour egg mixture over mixture in pie plate, pressing croissants down to submerge in egg mixture. Cover tightly, and chill 8 to 24 hours.
4. Preheat oven to 325°. Bake, covered, 35 minutes. Uncover and bake 25 to 30 minutes or until browned and set. Let stand 10 minutes before serving.