Preheat the oven to 375 degrees F. Lightly coat the sides and bottom of a 9 x 13-inch baking dish with cooking spray.
Cut the butter into small pieces, then place the pieces in the freezer while you prepare the dry ingredients.
In a large bowl, combine the 2 cups all purpose flour, white whole wheat flour, baking powder, baking soda, and salt.
Scatter the butter pieces over the top, then cut in the butter using your fingers or a pastry blender until the mixture resembles a coarse meal. The butter does not need to be uniform—some of the pieces may be the size of pebbles while others can be as large as your thumbnail.
Pour 1 1/2 cups, plus 2 tablespoons of the buttermilk over the top and gently mix with a rubber spatula until the mixture just begins to come together. If the dough seems overly dry, add 1 additional tablespoon of buttermilk. It should be moist, but not sticky.
Scrape the dough onto a lightly floured work surface and pat it flat. With a floured rolling pin, roll the dough into a 16 x 12-inch rectangle that is about 1/4-inch thick. Brush the surface of the dough with the 3 tablespoons of melted butter.
In a small bowl, stir together the granulated sugar, brown sugar, and cinnamon. Scatter the mixture evenly over the butter, leaving a 1/2-inch border on all sides. Sprinkle 1/2 cup of the chopped pecans on top.
Starting with the short (12-inch) side, roll the dough up tightly into a log, patting it as you go to help seal it. Trim 1/4-inch of dough off of each end so that they are even. With a very sharp knife, cut the log into 8 equal pieces. Arrange the rolls in the prepared baking dish, spacing them evenly (they will expand when baked).
Bake until puffed, golden brown, and flakey, about 25 to 35 minutes.
While the rolls bake, prepare the glaze. In a small bowl, whisk together the powdered sugar, vanilla extract, and 2 tablespoons buttermilk. If you desire a thinner glaze, add a little more buttermilk, until your desired consistency is reached. Drizzle over the warm rolls, then sprinkle the remaining 1/4 cup chopped pecans on top. Enjoy!
Notes
If using all purpose flour in place of the whole wheat flour, reduce buttermilk to 1 1/2 cups, adding 1 additional tablespoon if the dough seems too dry)
TO STORE: Biscuit Cinnamon Rolls taste best the day they are made but will last at room temperature for up to 2 days. Rewarm gently in the microwave.
TO FREEZE: Rolls can be frozen for up to 2 months.
TO MAKE AHEAD: Prepare through Step 5 up to 1 day in advance. Store it in the refrigerator, then when you are ready to bake, start at Step 4 (rolling the dough), then bake as directed. Another option would be to form the rolls all the way up through step 8 (before they go in the oven) and store them in the refrigerator in the baking pan for a few hours. Let the rolls stand at room temperature for about 10 minutes, then bake as directed.