Add canola oil, egg, egg yolk, and vanilla extract and stir until batter is combined (it will be a bit dry and crumbly but all of the flour mixture should be moistened before proceeding).
Gradually add hot coffee or hot water (take care not to burn yourself!) and stir until liquid is completely incorporated into the batter and you have a smooth chocolate batter.
Evenly divide batter into prepared muffin tin, filling liners between ½ and not more than ⅔ of the way full, this is typically about 3 Tablespoons of batter or less per cupcake liner.
Transfer one pan of cupcakes to 350F (175C) preheated oven and bake for 17-19 minutes or until a toothpick inserted in the center comes out with a few moist crumbs (or clean).
Allow to cool for 10-15 minutes in baking pan before carefully removing to cooling rack to cool completely before frosting. Repeat with second pan of cupcakes.