Pre-heat the grill to its highest setting.
Then toast the slices of bread on one side only. Now butter them on the untoasted side, right up to the edges, and sprinkle a tablespoonful of sesame seeds over each slice to cover as evenly as possible, pressing the seeds down so they will stay in position. Return the bread to the grill. Toast the sesame-encrusted side until the seeds are lightly toasted and the bread itself goes golden brown. Then cut each slice into four squares and eat straightaway with the piping hot soup,