Preheat the oven to gas mark 4/180oC/350oF/160oC fan and line a 12-muffin/cupcake tin with paper cases.
In a mixing bowl, cream together the caster sugar and butter until smooth. Add the vegetable oil and continue to mix. Whisk in the eggs and vanilla extract then mix in the milk and sour cream. Sift in the salt and self raising flour then 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.