SWISS ONION BREAD

Steps:

• In a large bowl, dissolve yeast in 1/2 cup warm water. Add 1 teaspoon sugar; let stand for 5 minutes. Add the butter, onion, egg, salt, mustard, 3 cups flour and remaining water and sugar. Beat until smooth. Stir in cheese and enough remaining flour to form a soft dough. , Turn onto a floured surface; knead until smooth and elastic, about 8-10 minutes. Place in a greased bowl, turning once to grease top. Cover and let rise in a warm place until doubled, about 45 minutes. , Punch dough down. Turn onto a lightly floured surface; divide in half. Roll each portion into a 18x10-in. rectangle. Cut in half lengthwise. Combine filling ingredients; spread to within 1/2 in. of edges. Roll up each, jelly-roll style, starting with a long side; pinch seams to seal. Place two ropes, side by side, on a greased baking sheet. Twist ropes together; pinch ends to seal and tuck under. Repeat with remaining dough. , Cover and let rise in a warm place until doubled, about 45 minutes. Beat egg yolk and water; brush over twists. Sprinkle with a additional poppy seeds if desired. , Bake at 375° for 25-35 minutes or until golden brown. Remove from pans to wire racks to cool. Store in the refrigerator.