Begin by preheating your oven to 180°C (160°C for fan ovens) and line a cupcake tray with paper cases.
In a mixing bowl, combine the light brown sugar, vegetable oil, and eggs. Whisk them together until the mixture becomes smooth and well incorporated.
Gently fold in the pumpkin puree, infusing the batter with that unmistakable autumn essence.
In a separate bowl, sift together the self-raising flour, baking powder, salt, cinnamon, mixed spice, ground ginger, and nutmeg. Gradually incorporate the dry mixture into the wet ingredients, stirring until a smooth batter forms.
Spoon the batter into the prepared cupcake cases, filling each one about two-thirds full. This allows room for the cupcakes to rise beautifully in the oven.
Place the cupcake tray in the preheated oven and bake for 20-25 minutes or until a toothpick inserted into the center comes out clean. Once baked, transfer the cupcakes to a wire rack to cool completely.
In a mixing bowl, beat the softened butter until it becomes light and fluffy.
Gradually sift in the icing sugar, combining it with the butter to create a smooth, creamy consistency.
Add vanilla extract, cinnamon, and milk to the butter and sugar mixture. Beat the ingredients together until the frosting achieves a luscious texture.
Once the cupcakes are completely cooled, generously frost each one with the prepared buttercream. You can use a piping bag for a professional touch or simply spread it with a knife for a rustic feel.