Preheat your oven to 170ºC (340ºF) and prepare two 8-inch round cake pans lined with parchment paper.

In a large mixing bowl, sift together all-purpose flour, cornstarch, baking powder, baking soda, and salt. Add cardamom, cinnamon, ginger, allspice, nutmeg, and black pepper. Whisk thoroughly.

In a stand mixer, cream butter with granulated and dark brown sugars until light and fluffy, about 3 minutes.

Add eggs one at a time, mixing well after each addition until the batter is smooth.

Gradually mix in the dry ingredients, alternating with sour cream, vegetable oil, and vanilla extract until just combined.

Pour the batter evenly into the prepared pans and bake for 28-30 minutes until a toothpick comes out clean.

Let the cakes cool in the pans for 5 minutes, then transfer to a wire rack to cool completely.

For frosting, beat together softened butter, powdered sugar, dark brown sugar, cream cheese, and vanilla bean paste until smooth.

Once the cakes are cool, assemble by leveling the tops and frosting between the layers and the exterior.

Decorate with a light dusting of cinnamon and star anise before serving.