Preheat the oven to 170°C fan bake. Line a 12-cup muffin tin with cupcake cases.
Cupcakes: Cream together the butter, sugar and vanilla until light and fluffy. Add the eggs one at a time, beating well after each addition.
Add half of the milk and mix to combine. Sift in the flour and baking powder and fold everything together.
Add the oil and remaining milk, then gently fold everything together until just combined.
Distribute the mixture evenly between the 12 cupcake cases.
Bake for 15 - 18 minutes until the cupcakes are just starting to colour on top and are cooked through. Once cooked, remove from the oven and allow to cool while you make the icing.
Icing: Whip the softened butter for 2 minutes until pale. Add the icing sugar, milk and vanilla essence. Whip on a high speed until light and fluffy, scraping down the sides as you go.
Spread or pipe the icing over the cooled cupcakes then add the sprinkles.
