With the paddle attachment of your mixer, beat butter and cream cheese for 2 to 3 minutes until fluffy and light, then add the sugar gradually and beat for another 2 minutes. Beat in salt, vanilla and egg yolk. 

Stir together flour, cornstarch and baking powder and sieve over the batter. Combine everything into a smooth dough. Roll out dough between 2 layers of cling film. You are aiming at a rectangle of about 20x30 cm.The dough should be quite easy to work with. Should it crack, smooth the dough out with your fingers.

In a small bowl, combine sugars, spices and salt. Melt the butter in the microwave and brush rectangle with the butter. Sprinkle the sugar mixture on top, saving about 2 tbsp for later. 

 Roll the dough up tightly– and very slowly, using the cling film as a help. Wrap the log tightly in cling film and chill for 3 to 4 hours. The chilling is the most important step as it prevents the cookies from spreading too much in the oven and losing their cinnamon roll shape! You are also not gonna be able to cut them neatly if not chilled properly, so do not rush this.

Preheat the oven to 180 C. Remove cling film and cut cookies into slices of about half a centimetre thickness. Bake for 12 minutes and let cool on a rack. Enjoy!