Essentially, caramel is sugar that has been melted and browned. The ingredients vary depending on whether the caramel is hard, gooey, or soft, but two ingredients remain king: milk and sugar.
Flan is found in recipes as far back as ancient Rome. It was during Roman times that domesticated chickens were first kept for laying eggs. The Romans, with eggs in surplus, and consulting the Greek’s knowledge of the art of cooking, developed new recipes, one of which turned out to be a custardly concoction known as flan.
Caramel custard is a variant of plain custard (crème) where sugar syrup cooked to caramel stage is poured into the mold before adding the custard base. It is usually cooked in a bain-marie on a stove top or in the oven in a water bath. It is turned and served with the caramel sauce on top, hence the alternate French name crème caramel renversée.