Preheat the oven to 350 F, and spray a 9-inch square baking pan with non-stick spray.
Using an electric mixer (stand or handheld), beat the sugar and butter for about 5 minutes, until light and fluffy. Scrape the bowl down and beat in the eggs.
Whisk in the sour cream, heavy whipping cream and extracts, until well combined.
In a separate bowl, sift together the flour, corn starch, baking powder, baking soda, salt, nutmeg and cloves.
Add the dry ingredients to the wet, and whisk briefly, just to combine. Use a spatula to finish folding in any bits of flour. The batter will be thick but spreadable.
Set aside while you make the filling.