Preheat oven to 350°F. Spray two medium (9 x 5) loaf pans with nonstick baking spray.
In a medium bowl whisk together flours, baking powder, and salt. Set aside.
In the bowl of a stand mixer beat the butter and the sugars until light and fluffy, about two minutes. Mix in Biscoff spread. Add eggs one at a time mixing well after each addition, scraping down sides of bowl as needed. Add vanilla and sour cream and mix to combined. Add flour mixture mixing on low just until combined.
Spoon batter into prepared pans. Bake for 50 minutes or until the center springs back when lightly pressed and toothpick comes out clean.
The nutrition information provided are only estimates based on an online nutritional calculator. This is not a comprehensive list of all the nutrients in the recipe (i.e., does not include vitamins, cholesterol, etc). I am not a certified nutritionist. Please consult a nutritionist or doctor for accurate information and any dietary restrictions and concerns you may have.