The pie of the Low Countries

Could the type of pastry, maybe, define what is a vlaai? Sadly not, because although they most commonly have a yeast-raised pie dough originally made with sifted rye flour, they can also be made with a richer shortcrust pastry. Today they are usually only made partially with sifted rye flour or completely with white wheat flour. The older recipes don’t even define the pastry. People would have used a sturdy dough of water and flour and maybe a little fat. Some pies wouldn’t have had, and still today don’t have, a crust at all.