In a mixing bowl, dissolve the yeast in warm water. Add the buttermilk, butter, sugar, egg, salt and baking soda; mix well. Stir in the flour to form a soft dough. Turn onto a floured surface; knead the dough until it is smooth and elastic (incorporating a sprinkle or two more flour, as needed), about 6 to 8 minutes. Place the dough in a greased bowl, turning once to grease the top. Cover the bowl with a clean dishtowel and let it rise in a warm place until it has doubled, about 1½ hours.
Punch the dough down. Turn it onto a lightly floured surface. Roll into a 18 x 9 inch rectangle; brush with the melted butter. Combine the brown sugar and the cinnamon; sprinkle over the dough. Fold in half lengthwise, forming a 18 x 4½ inch rectangle; pinch edges to seal. Cut into 4½ x 1 inch strips (using a pizza cutter is easiest) and place them 2 inches apart on greased baking sheets (or silpat lined). Twist each strip two or three times. Cover the baking sheets loosely with a clean dishtowel and let rise in a warm place until doubled, about 30 minutes.
Preheat the oven to 375°F. Bake twists for 12 to 15 minutes or until golden brown. Remove from pans to wire racks to cool. Whisk together the glaze ingredients; drizzle over warm twists.
Notes
Warm buttermilk will appear curdled, but this is normal.
These can be frozen! Wrap each individually in foil, defrost at room temperature when ready to eat.