Preheat oven to 170 °C (340 °F) conventional. Line two 20 cm (8‑inch) cake pans with parchment.

Sift together flour, cornstarch, cardamom, cinnamon, ginger, allspice, nutmeg, black pepper, baking powder, baking soda, and salt.

In a mixer, cream butter with granulated and brown sugar on medium‑high speed for about 3 minutes until light and fluffy.

Add eggs one at a time, mixing until combined. Scrape bowl as needed.

Add half of the dry ingredients on low speed, mix until just combined. Then add sour cream, oil, and vanilla, mixing until just incorporated. Add remaining dry mix and stir gently. Finish with a light fold by hand.

Divide batter evenly into prepared pans. Bake for 28–30 minutes or until a tester comes out clean. Let cool in pans 5 minutes, then transfer to wire rack to cool fully.

For the frosting: sift powdered sugar. Cream butter, powdered sugar, and brown sugar on high speed 3 minutes. Scrape and mix another minute.

Add vanilla bean paste and cream cheese on low speed, mixing for 1 minute. Finish by hand to remove air bubbles.

Trim cake layers to level tops. Place first layer on serving plate, add three large scoops of frosting, smooth. Top with second layer, apply a thin crumb coat. Scrape sides lightly for a semi‑naked finish.

Decorate with dusted cinnamon, star anise and cinnamon sticks if desired. Chill briefly before serving.