Preheat the oven to 180°C (350°F) and line 2x 12-hole cupcake pans with cupcake liners.
Add the butter, oil, and sugar to a bowl of an electric mixer fitted with a paddle attachment. Beat until light and fluffy.
Add the eggs to the sugar and butter mixture one at a time. Beat well between each addition and scrape down the sides of the bowl often.
In a large bowl sift together the flour, salt, and cocoa powder.
In a jug mix together the cooled coffee, sour cream, milk, and vanilla.
With the mixer’s motor running at medium-low speed, add the wet ingredients and the flour mixture to the egg and sugar mixture. Do this by alternating between the two. Starting with the flour and ending with the wet ingredients.
Using a rubber spatula scrape down the sides of the bowl and mix the cupcake batter again. Ensuring that it is well-mixed and lump-free.
Using a jug or ice-cream scoop pour the chocolate cupcake batter into the prepared cupcake liners and bake in a preheated oven for about 12 - 15 minutes or until a skewer inserted into the center of a cupcake comes out clean.
Allow the cupcakes to cool in their tin for about 5 minutes before transferring them to a wire rack to cool completely.
Dulce de Leche Frosting
Add the icing sugar and butter to a bowl of a stand mixer fitted with a paddle attachment. Beat at medium speed until the mixture resembles fine breadcrumbs.
Add the cubed cream cheese and beat at medium-high speed until the frosting is smooth and fluffy. Scrape down the sides of the bowl and mix again for about 2 minutes.
Add the dulce de leche, vanilla, and salt to the frosting and beat again at high speed.
Scrape down the sides of the bowl with a rubber spatula and beat at medium-high speed for a further 3 minutes or until the frosting is light and fluffy. Add the frosting to a piping bag fitted with your chosen nozzle. Add the remaining dulce de leche to a plain piping bag.
Pipe a swirl of frosting onto each cupcake and then pipe a dollop of caramel on top of the frosting. Decorate with chocolate shavings, serve, and enjoy!