The cookies were invented in the city of Vlaardingen and are baked on a checkered iron plate, creating a characteristic waffle-like pattern, similar to stroopwafels.

According to oral history, the grocer "Daatje de Koe" (1838–1915) made the first Vlaardingse iron cookies.

Research of the Vlaardingen baker Hazenberg in regional archives showed that the cookie is probably older and dates from the 18th century.

Also, special waffle irons are available as well as ijzerkoekje flour for baking the cookies at home.

The cookies are called 'ijzer' or 'ijzer koekje' and are made with wheat flour, sugar, egg, coconut milk, cinnamon, cloves and salt.