Dissolve yeast with 2 tsp. sugar in 1/4 c. warm water. Melt butter. In a large bowl, put 1/2 cup sugar, salt, 2 cups water. Add melted butter, then slowly beat in eggs. Add yeast mix. Gradually add flours; knead till smooth.
Wash bowl with warm water, butter sides. Put dough back in, turn so butter side is up. Let rise, covered, for 1 1/2 hours or till doubled. Punch down; let rest 3 to 4 minutes. Divide dough in half (or in thirds) and shape into two (or three) braided loaves on greased cookie sheet.
Cover and let rise for 45 minutes. Brush with beaten eagg. Bake at 375 for 15 minutes, reduce heat to 350 and bake for another 15 minutes. Cool at least 10 minutes before cutting.