Lyon charcutiers sell it plain or with pistachio- or truffle-studded sausage inside the brioche.
A whole Lyon cooking sausage baked inside soft, golden brioche dough, then cut into thick slices at charcuterie counters such as those in the Halles de Lyon Paul Bocuse.
Why it's made this way: It is a classic of Lyonnaise cuisine, a Sunday family dish built on the city’s own saucisson chaud (cooking sausage).