Preheat the oven to 325°F. Generously grease and flour a 10-cup Bundt pan. Or spritz with Baker's Joy (my go-to).
Add the cake mix, cinnamon, and salt to a large mixing bowl. Whisk to combine.
Add the vegetable oil, sour cream, evaporated milk, cookie butter, and vanilla. Mix on low speed until just combined.
Add the eggs one at a time, mixing between each addition. Increase the mixer to medium speed and beat for 30-45 seconds. Scrape down the sides and bottom of the bowl and give the batter a final stir by hand.
Fold in 1 cup crushed Biscoff cookies until evenly distributed. Do not overmix.
Spoon the batter evenly into the prepared Bundt pan and smooth the top.
Bake for 55-60 minutes, or until a toothpick inserted into the thickest portion of the cake comes out clean or with just a few moist crumbs.
Remove from the oven and allow the cake to cool in the pan for 10-15 minutes.
Carefully invert the cake onto a wire rack and allow it to cool completely before frosting.
To make the frosting, beat the softened cream cheese and butter until smooth and creamy. Gradually add the powdered sugar, vanilla, and salt. Beat until smooth. Add heavy cream or evaporated milk, a little at a time, only if needed to reach a thick, pipeable consistency.
Pipe thick ribbons of cream cheese frosting from the outside edge of the cake toward the center.
Microwave the ¼ cup cookie butter for about 10-15 seconds, or just until it loosens enough to drizzle. Drizzle over the frosting and finish with crushed Biscoff cookies.