Preheat the oven to 180 degrees Celsius or 350 degrees Fahrenheit.
Rub butter into flour until it gives a coarse mixture.
Add egg yolk, breadcrumbs, parmesan cheese, salt and pepper, and water, and mix together. Add a tablespoon of water if you find them difficult to bind.
Shape dough into golf ball size.
Dip into slightly beaten egg white.
Place in a well oiled baking sheet and bake in the oven for 25 minutes or until brown and crispy.
Invert the balls as well baking this time for 5 minutes or until brown and crispy too.