In your mixer fitted with the dough hook, combine the yeast, ginger, sugar, and warm water.
Allow to get puffed up and foamy (about 5 minutes).
Combine the buttermilk, honey, salt and baking soda together, then add it to the yeast mixture.
Add 3 cups of the flour and mix until smooth.
With the mixer on low, add the melted butter and remaining flour.
Knead on low until the dough becomes smooth and elastic, about 8-10 minutes.
Remove from mixer, and turn out onto a floured surface.
Grease a large bowl, and add the dough to the bowl.
Cover, and rise for 1.5 hours (it needs to double in size)
Punch down and divide into 2.
Shape into loaves, and add to 2 buttered bread tins (or glass pans).
Cover with a clean kitchen towel and leave somewhere warm for about 30 minutes.
Preheat the oven to 400F.
Cover the loaves loosely with tinfoil to prevent browning too fast, and bake for 30 minutes.
Remove the loaves from the oven and brush with the extra butter (if using)
Allow to cool completely on a wire rack (covered with a kitchen towel)