Preheat oven to 175°C and prepare a cupcake pan with muffin liners (or cupcake liners).
Whisk together self-raising flour, cocoa powder, pumpkin spice powder, baking powder and salt in a mixing bowl. Sift the mixture and set it aside.
In another bowl, combine sugar and butter. Cream until light and fluffy (about 2 minutes on medium speed). Scrape the sides and bottom of the bowl halfway through.
Beat in the eggs, one at a time until well incorporated. Scrape the bowl's sides and bottom halfway through to ensure thorough mixing (see Note 1).
Add the pumpkin puree and beat until well combined. The mixture will curdle and that is fine.
Gradually fold half of the flour mixture (dry ingredients) into the creamed wet ingredients. Do not overmix.
Add the milk and fold again, followed by the remaining flour mixture. Scrape the sides and bottom of the bowl.
Add the vanilla extract and mix well.
Scoop the batter into the prepared cupcake liners (see Note 2). Fill each liner about three quarters full.
Bake the cupcakes for 15 - 18 minutes or until a toothpick inserted into the center of the cupcakes comes out clean without any wet batter (see note 3).
Remove the cupcakes from oven and let them rest in the tin for 1 to 2 minutes before transferring them to a cooling rack to cool completely to room temperature before decorating. Keep the cupcakes covered in a kitchen towel (see Note 4).