Preheat the oven to 200C, fan-forced. Line an oven tray with baking paper. Peel the pumpkin and cut into 5cm chunks. Put on the lined tray and bake for 40 mins or until tender. Meanwhile, grease an 18cm round springform pan and line the base and side with baking paper.
Step 2 — Mash pumpkin
Mash the pumpkin with a fork on the tray. Spread into a thin layer and stand for 5 mins to cool. Fold the baking paper with the pumpkin layer in half, then gently press the pumpkin to mash more thoroughly.
Step 3 — Make cake batter
Reduce the oven to 180C. Put the mashed pumpkin, vanilla cake mix, 1¼ tsp mixed spice, 180ml (¾ cup) milk, 60ml (¼ cup) vegetable oil and 1 egg in a large bowl and whisk for 1 min or until well combined.
Step 4 — Bake cake
Pour the batter into the pan. Bake for 45-50 mins until golden and a skewer inserted into the centre comes out with a few moist crumbs clinging. Cool in the pan for 15 mins, then transfer to a wire rack to cool completely.
Step 5 — Ice cake and serve up
Combine half the icing sugar* and 2 tsp milk in a bowl (see Make it spiced). Drizzle the cake with the icing and sprinkle with the remaining mixed spice. Cut the cake into wedges to serve. Serves 8-10.
Step 6 — Make it spiced
You can add the remaining mixed spice to the icing instead of sprinkling it over the cake at the end.