In a large bowl, dissolve yeast in warm water. Add the buttermilk, butter, sugar, eggs, salt, baking soda and 5 cups flour. Beat until smooth. Stir in enough remaining flour to form a soft dough.
Turn 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 1-1/2 hours.
Punch dough down. Turn onto a lightly floured surface; divide in half. Roll each into a 16-in. x 9-in. rectangle; brush with butter. Combine brown sugar and cinnamon; sprinkle over dough.
Fold in half lengthwise, forming a 16-in. x 4-1/2-in. rectangle; pinch edges to seal. Cut into 4-1/2-in. x 1-in. strips; twist each strip two or three times. Place 2 in. apart on greased baking sheets. Cover and let rise until doubled, about 30 minutes.
Bake at 375° for 12-14 minutes or until golden brown. Remove from pans to wire racks to cool. Combine glaze ingredients; drizzle over warm twists.