The rusk is one of the
iconic foods of
South Africa, one of the things that
expatriates and
travellers miss most along with
biltong,
boerewors,
Peppermint Crisps,
Karoo lamb and Mrs Ball's
chutney.
Legend has it the rusk was brought to perfection by the Voortrekkers (for the Americans: think wagon train), who dried their bread out after baking to preserve it for long journeys. The rusks in my kitchen cupboard are marketed under the name "Ouma" (Grandmother) with a long spiel about farmers' wives baking to fund the Boer War, which gives you some idea of the kind of cultural space they occupy.
Unless you're good and support your local home industries shop, the modern rusk is mass-produced and comes in several flavours including wholewheat, caramel and muesli. Otherwise it's unchanged, a fist-sized hunk of sweet, milky bread dried to extreme hardness in a coolish oven.
The only way to render a rusk edible is to dunk it in a cup of hot coffee and then eat the soggy bit off the end, repeating until the rusk is gone. You'll have to take my word for it that this is a deeply satisfying gastronomic experience -- both the rusk and the coffee, which in South Africa is famously awful, benefit from the interaction.