Preheat your oven to 180°C (160°C fan) and line a 20cm square baking tin with parchment paper. Let the paper overhang on two opposite sides — this creates handles that let you lift the whole cake out cleanly later. The room will start to smell warm and inviting as the oven heats.

In a large mixing bowl, whisk together the flour, both sugars, baking powder, bicarbonate of soda, pumpkin spice mix, and salt. Use a balloon whisk to break up any lumps in the brown sugar. The dry mixture should look uniform in colour, with the darker sugar flecks evenly distributed through the pale flour. Set the bowl aside.

In a separate jug or small bowl, combine the pumpkin purée, vegetable oil, eggs, vanilla extract, and milk. Whisk vigorously until the mixture is completely smooth and a vibrant, deep orange colour. It should have a thick, pourable consistency, similar to a thin milkshake. The earthy, sweet scent of pumpkin will rise as you mix.

Pour the wet ingredients into the bowl of dry ingredients. Stir gently with a spatula or wooden spoon, folding the mixture together until no streaks of flour remain. Stop as soon as the batter comes together — about 12 to 15 strokes. The batter will be thick, glossy, and slightly tacky, clinging to the spatula in soft ribbons.

Scrape the batter into the prepared tin and spread it evenly to the corners. Use the back of the spatula to smooth the top. The batter should sit about halfway up the sides of the tin. Tap the tin once on the work surface to release any trapped air bubbles — you will see a few tiny pops appear on the surface.

Bake for 28 to 32 minutes, or until the top is a deep golden brown and springs back when lightly pressed in the centre. A skewer inserted into the middle should come out clean or with a few moist crumbs attached, not wet batter. The kitchen will fill with the unmistakable aroma of cinnamon, ginger, and nutmeg. If the top is browning too quickly after 25 minutes, loosely cover it with a sheet of foil.

Remove the tin from the oven and place it on a wire cooling rack. Let the cake cool in the tin for 10 minutes. Using the parchment overhang, lift the cake out and set it directly on the rack to cool completely. The surface will feel firm and slightly crisp, while the interior remains tender and steamy.