Combine Dry Ingredients: In a medium bowl, whisk together the plain flour, cocoa powder, bicarbonate of soda, 1 teaspoon of the ground cinnamon, nutmeg, cayenne pepper, and salt. Whisking is important as it distributes the spices and leavening agent evenly. Set aside.

Cream Butter and Sugars: In the bowl of a stand mixer fitted with the paddle attachment, or using a hand mixer, beat the softened unsalted butter, light brown sugar, and 100g of caster sugar on medium-high speed for about 3-4 minutes. The mixture should become pale, light, and fluffy. For a deep dive into why this step is so important, Serious Eats has a great guide on the science of creaming butter and sugar.

Add Eggs and Vanilla: Add the eggs one at a time, beating well after each addition until fully incorporated. Scrape down the sides of the bowl as needed. Beat in the vanilla extract.

Combine Wet and Dry: Reduce the mixer speed to low and gradually add the flour mixture. Mix only until the last streaks of flour have disappeared. Be careful not to overmix, as this can result in tough cookies.

Chill the Dough: Cover the bowl with cling film and refrigerate for at least 1 hour, or up to 3 days. What works best for me is chilling it for a full 90 minutes for the firmest dough and deepest flavour.

Prepare for Baking: When you're ready to bake, preheat your oven to 180°C (160°C fan) and line two large baking trays with parchment paper.

Make the Topping: In a small, shallow bowl, mix together the 50g of caster sugar and the remaining ½ teaspoon of ground cinnamon.

Shape the Cookies: Scoop out portions of the chilled dough (about 1.5 tablespoons each) and roll them into smooth balls. Roll each ball in the cinnamon-sugar mixture until it's evenly coated.

Bake to Perfection: Place the dough balls on the prepared baking trays, leaving about 5cm (2 inches) of space between them to allow for spreading. Bake for 10-12 minutes. The edges should be set, but the centres will still look slightly soft and underdone. This is the secret to a fudgy middle.

Cool Down: Let the cookies cool on the baking trays for 5 minutes before transferring them to a wire rack to cool completely. They will firm up as they cool.