Preheat the oven to gas mare 4/180oC/350oF and line a 12-muffin/cupcake tin with paper cases.
In a mixing bowl, cream together the caster sugar and butter until smooth then add the vegetable oil and continue to beat.
Beat in the eggs, vanilla extract, milk and sour cream then sift in the self raising flour and mix until fully combined.
Spoon the batter into the paper cases making sure they are ⅔ filled. Bake for 23 minutes or until a light brown and a cake tester comes out clean. Leave to cool for 10 minutes then transfer cakes to a wire rack to completely cool.
For the frosting, pour the cream into a stand mixer bowl or a mixing bowl and add vanilla and icing sugar. Whisk on a medium speed using the stand mixer or a hand held mixer until the cream forms fluffy peaks. If you do not have a stand mixer or a hand held mixer, you can use an 8-wire whisk.
Spoon the whipped cream into a piping bag with any shaped nozzle inside and pipe the whipped cream frosting onto the cupcakes. Decorate with strawberries. If not serving straight away then ensure you refrigerate these cupcakes immediately after you frost them.