Preheat oven to 350 degrees F (180 degrees C) or 320 degrees F (160 degrees C) for a fan-forced oven. Line a cupcake tin with cupcake liners.
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 the softened butter and let it mix until it resembles a fine sand-like texture.
Next, add milk, eggs, yogurt, oil and vanilla to a mixing bowl with a spout and whisk well.
Add wet ingredients to dry ingredients in a slow and steady stream until no dry ingredients are visible. Scrape down the bowl and mix for another 20 seconds.
Fill cupcake liners 3/4 of the way full. (Tip: Use an ice cream scoop to transfer the batter.) Bake for 20 to 25 minutes, or until a toothpick inserted comes out clean. Allow cupcakes to cool completely on a wire rack before frosting.
Once the cupcakes have baked and cooled, dip the tops in the coffee mixture. Give them a gentle tap to help the coffee soak into the cake.
Core the center of each cupcake and fill with chocolate sauce.
To frost the cupcakes, you'll need hot water, an ice cream scoop and paper towels.
Dip the ice cream scoop into the hot water, dry it off well and scoop up some frosting. Gently press the scoop onto the top of the cupcake to help the frosting stick to the cake, then release the scoop. Decorate with two coffee beans on top.