Preheat the oven to 170°C and line two cupcake trays with 24 cupcake papers.
Add the oil, sugar, and eggs to a bowl of an electric mixer fitted with a whisk attachment and mix until well combined.
Sift the flour and salt together, and add this to the egg mixture, beat briefly on high speed until combined.
Add the vanilla to the milk and slowly add this to the flour mixture, while the beater is going. Continue until all of the milk has been added. Scrape the sides of the bowl and mix again to ensure everything is well combined and there are no lumps.
Pour the mixture into a jug and fill the cupcake papers ¾ of the way. Bake in a preheated oven for about 12 to 15 minutes or until cooked. Allow the cupcakes to cool.
Salted Caramel
Add the sugar to a small pot set over medium heat. Whisk until the sugar has melted.
Allow the sugar to turn an amber colour and then add the cream. The caramel will bubble so be careful. Once the cream has been mixed in, add the cubed butter and whisk the caramel until it is well combined. Whisk through the sea salt.
Pour the caramel into a glass jar and allow the caramel to cool. Once cooled, keep ¾ of a cup for the buttercream and place the remainder of the caramel in a piping bag, for the hidden centre of the cupcakes.
Salted Caramel Buttercream
To make the frosting, combine the butter and the icing sugar in a bowl of an electric mixer fitted with a paddle attachment. Beat until combined.
Add the vanilla to the cream and slowly add this to the icing sugar mixture, while beating at high speed. Scrape down the sides of the bowl to ensure everything is mixing evenly.
Add the cooled homemade salted caramel to your buttercream and mix again.
Continue mixing until the frosting is fluffy, add to your piping bag fitted with your chosen nozzle.
To assemble the cupcakes, use an apple corer to remove the centre of the cupcake. Fill the centre with the caramel from the piping bag. Pipe a swirl of buttercream on each cupcake and top with pieces of Crunchie chocolate.