Preheat the oven to 170 C (fan). Line up your muffin tray with liners.
In a medium bowl, sift together the flour, all the spices, baking soda, baking powder and salt. Mix it all with the whisk to combine.
In a large bowl of the standing mixer, beat together butter and both sugars on a medium speed until light and fluffy. Add the oil in a slow stream, mix well. Add the eggs, one at a time, mixing well after each addition, then add the pumpkin puree. Continue beating until you have a smooth mixture. Tip in half of the flour mixture, reduce speed to low, beat until just combined then add the milk and mix again. Add the remaining flour mixture and beat until just combined.
Divide the mixture between your muffin cases, filling about 3/4 of each case.
Bake for 20 minutes or until toothpick inserted to the middle comes out clean. Allow the cupcakes to cool completely before topping with the frosting.
For the frosting
Beat the butter in a large bowl of a standing mixer fitted with the paddle attachment until light and fluffy. Sift in the icing sugar, spices, salt and vanilla extract. Beat until the mixture is soft and creamy. Depending on the consistency, you may want to add a some milk (no more than a tablespoon) to loosen it up a bit.
Transfer the frosting into a piping bag fitted with your favourite nozzle and top the cooled cupcakes with he frosting. Sprinkle with some ground cinnamon. Enjoy!