Gather all your ingredients so that you have everything close at hand on the counter or table.
In a large mixing bowl, combine the sourdough starter, warm water, granulated sugar, olive oil, instant yeast, salt, and bread improver. Add in instant potato flakes, whole-wheat flour, Harvest Grain Blends, and all-purpose flour.
Beat with dough hook and mix until combined. Continue to knead for 5 minutes. Place dough in a greased bowl and cover with plastic wrap coated with baking spray. Allow to rise for 60-90 minutes until double.
Grease an 8" x 4" loaf pan. Turn the dough out onto a lightly floured surface, and pat into a rectangle. Roll and shape it into a log to fit the pan. Pinch edges and ends together to seal. Place in pan and cover with plastic wrap coated with baking spray. Allow to rise until double, 60-90 minutes.
Bake in a preheated 350F degree oven and bake for 35 minutes until golden brown. Remove from oven and turn out onto wire rack to cool. Makes 1 loaf.