Melt the Butter: Melt butter in a small saucepan over low heat, stirring occasionally. Alternatively, melt in the microwave in 30-second intervals.
Cool the Butter: Pour melted butter into a large mixing bowl and let cool for 5–10 minutes until only slightly warm. Ensure it doesn’t firm back up.
Mix Sugars: Add both sugars to the slightly warm butter and whisk for 20 seconds until combined. The mixture will thicken gradually; avoid leaving it too long as it will become harder to whisk in the egg.
Add Egg and Vanilla: Whisk in the egg and vanilla until smooth, about 15 seconds.
Sift Dry Ingredients: Sift flour, cornstarch, baking soda, cardamom, cinnamon, allspice, cloves, nutmeg and ginger over the wet mixture. Add the salt. Fold through with a spatula until a thick cookie dough forms.
Chill the Dough: Cover and chill the dough in the refrigerator for 45 minutes. If the bowl is too large, wrap the dough and refrigerate.
Preheat the Oven: While the dough chills with 20-30 minutes remaining, preheat oven to 356ºF (180ºC). Line a large baking sheet with parchment paper. Set aside.
Shape Cookies: Scoop and weigh 45g (1.5 oz) of dough per cookie (about 3 level tablespoons if no scale). Roll into a cylinder shape (slightly taller than wide) and place on the lined tray without flattening.
Arrange on Tray: Space dough balls 10cm (4 inches) apart to allow spreading. Bake in batches, as they won’t all fit on one tray.
Bake: Bake for 8-9 minutes until edges are lightly golden. Centers may look slightly underbaked, this keeps them soft and chewy.
Cool Cookies: Remove from oven and let cool on the tray for 10 minutes, then carefully transfer to a wire rack to cool completely.