The Galette-Saucisse is a grilled pork sausage wrapped in a buckwheat galette, and it is the closest thing Brittany has to a hot-dog vernacular: a single sausage, a single sheet of bread, no plate, no fork. A plain pork sausage is grilled until its skin blisters, a buckwheat galette is cooked thin on a hot iron, and the sausage is rolled inside it lengthwise so the bread closes around it as a sleeve. There is no bun, no split roll, no condiment built in by default. The galette is the wrapper and the hand-hold at once.
The construction is what separates it from the rest of the Breton galette tradition. The folded galettes, with ham and cheese and egg, are plated and eaten with cutlery. This one is rolled tight around the sausage so it can be eaten standing up, walked with, and bought from a stall, which makes it street food rather than table food. The buckwheat earns its place here too: its nutty, faintly bitter taste stands up to the fat and char of a grilled sausage in a way a soft white bun would not, and the thin galette wraps without the bulk a bun adds, so the sausage stays the main event. It is eaten the moment it comes off the grill, while the galette is still pliable and the sausage is hot, and it is a fixture of Breton markets, fairs, and the stands outside stadiums.
This is a Brittany street-food icon, and the plain version is the base from which the obvious variation departs. The most common one is a stripe of mustard added down the sausage before it is rolled, which gets its own treatment as the Galette-Saucisse Moutarde. The wider family keeps the buckwheat constant and changes what it wraps: ham and cheese and egg in the folded complète, smoked andouille in another corner, the sweet wheat-flour crêpe for dessert. Those relatives are gathered under Crêpe & Galette Salée, and the Galette-Saucisse is the one the family takes out of the house and eats on its feet.