The name means 'pre-oven': it was a scrap of dough baked to test the wood oven's heat, once thrown away or fed to animals.
A flat, unleavened bread split and filled with butter, chopped fresh garlic and pepper, warmed until golden and pulled apart as a snack with a drink.
Why it's made this way: Vendée bakers began adding garlic butter to their oven-test bread, and the garlic version stayed a southern Vendée bakery specialty until the 1980s.