Preheat oven to 350°F. Grease and flour a 10-inch fluted tube pan and set aside.

In a large mixing bowl or the bowl of a stand mixer, cream butter and sugar until light and fluffy. Add eggs, one at a time, beating well after each addition. Next, add in the vanilla extract to the creamed butter mixture.

In a medium-sized bowl, combine the white whole wheat flour, unbleached all-purpose flour, baking powder, baking soda, cardamom, allspice, and nutmeg. Add the flour mixture to the creamed butter mixture, alternating with the sweet potatoes. Beat until just combined, then add in the 2 tablespoons of milk and stir on low. Allow the mixture time to hydrate so let it rest for 10-15 minutes. In the meantime fix the streusel topping.

In a medium-sized bowl, combine the flour, brown sugar, and cinnamon together. Cut in the cold butter with a pastry blender or a fork until the mixture forms coarse crumbs. Stir in the pecans.

In the prepared bundt pan, add half of the streusel topping and press into the bottom of the pan. Pour half of the cake batter on top of the streusel topping then smooth it around. Next, add the remaining streusel topping on top of the cake batter. Finish layering the pan with the remaining cake batter. Smooth it into around as best as you can then bake it for 1 hour or until an inserted toothpick comes out clean.

Remove the cake from the oven and cool the cake in the pan for 10-15 minutes before removing it from the pan to cool completely on a wire rack.

In a small saucepan set over medium heat, combine the butter, brown sugar, heavy cream, and bourbon. Bring to boil and boil for one minute. Remove from heat; let stand for 5 to 10 minutes. Whisk in the sifted powdered sugar until smooth. Immediately spoon the glaze over the cake as it is cooling.

Once the cake has finally cooled, cut and serve. Store in an airtight container at room temperature.