Dissolve yeast in 2 c lukewarm water. Add sugar, salt, starter, and flour. Cover; let rise to doubled. Roll out dough to 0.75 in thick. Cut with biscuit cutter. Dip both sides in butter. Place on well-greased baking pan. If touching will be soft, if not, will have crust. Let rise 15 min. Bake at 190ºC or 20 min.