Preheat your oven to 160C / 320F (fan on), 180C / 356F (fan off). Line a cupcake tin with cupcake liners.
Mix dry ingredients - In the bowl of a stand mixer fitted with the paddle attachment, add the flour, baking powder, caster sugar and salt. Turn mixer on low speed and allow it to mix for a couple minutes to help everything combine well (alternatively you may do this by sifting the ingredients together).
Add butter - Add the softened butter and let it mix until it resembles a fine sand like texture.
Add wet ingredients - Next, add the orange juice, eggs, oil, orange food gel and orange essence to the dry ingredients in a slow and steady stream until no dry ingredients are visible. Scrape down the bowl and mix for another 20 seconds.
Bake - Fill each cupcake liner 3/4 of the way (using an ice cream scoop to transfer the batter into the cupcake liners makes this a quick and easy process otherwise you can use two tablespoons). Bake for 30-35 min or until a toothpick inserted comes out clean. Allow them to cool completely on a wire cooling rack before frosting.
Frosting - To prepare frosting add orange food gel and orange essence to frosting and mix until well combined.
To decorate - Once baked and cooled core the centre and fill with chocolate sauce. Fit the end of a piping bag with a Wilton 1M tip and frost in a swirl. Finish with sprinkles.