Preheat oven to 325°
In a large bowl, combine the oil, both sugars, bourbon, vanilla, and eggs and stir with a spoon to mix. Then stir the grated apples.
In a separate bowl, whisk together the 2 cups flour, whole wheat flour, cinnamon, baking soda, and salt. Add dry ingredients to the apple mixture and mix only until it all comes together in a smooth batter.
Toss the apple chunks and chopped walnuts (if using) with the 1 tbsp all purpose flour and fold into batter.
Pour batter into prepared pan. Gently tap the pan on the counter several times to make sure the batter has fully settled into the nooks of the Bundt pan.
Bake until the testers comes out clean, about 1 hour-15 minutes. Let the cake cool in the pan for 15 minutes, then turn upside down and turn it out unto a cake plate.