In a stand mixer bowl, combine 1 1/2 cups flour, yeast, sugar, salt and baking soda; mix well. In saucepan or microwave-safe dish, heat buttermilk, water and shortening/butter until warm (120-130°F; shortening/butter does not need to melt). Add to flour mixture. Using a paddle attachment, blend on low speed for 30 seconds; beat on medium speed for 3 minutes.
Switch to dough hook attachment. Gradually stir in enough remaining flour to make a firm dough. Knead until smooth and elastic, about 5 to 8 minutes.(NOTE: For hand mixing: following above steps, mix ingredients in large mixing bowl using a wooden spoon or dough whisk. Knead on floured surface until smooth and elastic.)
Place dough in lightly oiled bowl and turn to grease top. Cover; let rise until indentation remains after poking dough with finger down to second knuckle, about 30 minutes.
Punch down dough. Divide into 4 equal parts. Divide each fourth into 6 equal pieces. Shape each piece into a smooth ball. Place in greased 15x10-inch jelly roll pan. Cover; let rise in warm place until almost doubled, about 20-30 minutes.
Preheat oven to 400°F.
Bake for 15 to 20 minutes until golden brown. Remove from pan and place on wire rack to cool.