Preheat oven to 350ºF.
In a large bowl, mix together, the oil, white sugar, and melted chocolate. Add in the egg and beat for a couple of minutes. Next, add in the sour cream and mix until incorporated.
Sift in the dry ingredients: flour, baking soda, baking powder, salt and cocoa powder.
Line cupcake tin with cupcake liners (about 12-14).
Bake at 350ºF for 15-18 minutes. Cupcakes are done when toothpick inserted comes out clean.
Cool cupcakes in cupcake tin for about 10 minutes, then transfer to wire rack to cool completely.