Sift the flour and salt into a large bowl. Add the yeast mixture and work into a dough. Put the dough into a greased bowl, cover with a damp cloth, and let rise until doubled in bulk, about 1 1/2 hours.

Punch dough down and divide into 20 pieces. On a floured board, shape each into a round roll, then transfer the rolls to 2 floured cookie sheets. Cover lightly with a cloth and let rise for 45 minutes.

Preheat oven to 400°F.

Chop the onions. Press your thumb into the center of each roll to make a shallow depression. Brush depression with the beaten egg mixture, and sprinkle with some chopped onion.

Sprinkle very lightly with flour. Bake rolls for 20 minutes, or until golden. Cool on wire racks. Serve split and buttered.