Ham and Cheese Spinach Puffs

sheets pre-made frozen puff pastry, thawed

butter

medium yellow onion, minced

all purpose flour

whole milk

salt and black pepper,

ground nutmeg

cooked ham, diced (see recipe notes section below)

fresh spinach, roughly chopped

Gruyere, shredded ((Swiss cheese may be substituted))

egg

water

fresh parsley, minced (for garnish)