Since Canadian flour has more gluten, I use whole wheat bread flour and all purpose white flour, if you reside in the U.S. then use bread flour for the white.
In the microwave warm the buttermilk, butter, 3 tablespoons sugar and 1-1/2 teaspoons salt for about 40 seconds until warm (the butter does not have to melt completely) then pour into the stainless steel mixing bowl with the flour.
05After the yeast is proofed, add into the bowl along with the 1/2 teaspoon baking soda and start mixing/kneading adding in more WHITE flour as needed to create a soft semi-sticky dough (because of the oatmeal and whole wheat flour the dough will be more sticky than usual).
06Knead for 10 minutes.
07Remove the dough to a lightly-floured surface; cover with a clean tea towel and let rest for 10 minutes.
08Gather up the dough and knead gently for about 15 seconds with your hands (it will come together nicely).
09Generously grease a large bowl with oil.
10Place the dough in the bowl, cover with plastic wrap or a clean tea towel and let rise for about 1 hour and 15 minutes (it might take more or less time depending on the temperature of your kitchen, or place in a warmed oven to rise).
11Remove and punch down dough.
12Place on a floured surface and roll out to about 14x8 inches (does not have to be exact size!).
13Roll up tightly and tuck the sides under to fit the 8x4-inch loaf pan (I just slice off the ends of the dough enough to fit into the pan and pinch the dough together, it makes for a more even loaf).
14Cover and let rise for about 30-45 minutes (depending on how warm your kitchen is) in a warm place covered with a clean tea towel.