Buckwheat Pancakes with Leek and Cheese Filling

Gaieties de sarrazin, buckwheat pancakes, are the ultimate fast food. In my mother’s home town of Vitré, there is a stall which sells galettes-saucisse every market day, and one of my greatest treats was to buy them for lunch. They never made it to the table, though; ideally they should be eaten hot, out of a paper cornet, on a street corner or park bench.