Preheat your oven to 350 degrees Fahrenheit (180 degrees Celsius) and line a 12 hole muffin tin with cupcake liners.
Combine milk and white wine vinegar in a jug and set aside to thicken.
Next, sift together flour, cocoa powder, baking powder, baking soda, sugar & salt into a bowl and stir with a whisk to combine.
In a second bowl, add oil, eggs, thickened milk & vanilla extract. Mix together using either a whisk, an electric handheld mixer or a stand mixer fitted with a whisk attachment.
Add the dry ingredients to the wet ingredients and stir together, then add the coffee.
Spoon the batter into your prepared cupcake liners and bake in the oven for 15-18 minutes or until cooked through (see notes).
Once baked, allow the cupcakes to cool in the muffin tin for about 5 minutes, then transfer to a wire rack to cool completely.
Optional step: Once cool use a knife to cut a hole in the center of each cupcake. Then carefully spoon some whiskey caramel into this hole.