In a mixing bowl, dissolve yeast in water. Add milk, onion, mustard, oil, sugar, salt and 4 cups flour; beat until smooth. Add enough remaining flour to form a soft dough. Turn out onto a floured surface; knead until smooth and elastic, about 6-8 minutes. Place in a greased bowl, turning once to grease top. Cover and let rise in a warm place until doubled, about 1 hour. Punch dough down; divide into 24 pieces Flatten each piece into a 3-in. circle. Place 1 in. apart on greased baking sheets. Cover and let rise until doubled, about 45 minutes. Bake at 350 degrees F for 20-25 minutes or until golden brown. Cool on wire racks.