Arrange rack to center of oven and preheat oven to 350F (175C). Line two 12-count muffin tins with paper liners.

In a large bowl, whisk together sugar, flour, cocoa powder, cornstarch, baking powder, baking soda, and salt (I make this recipe with an electric mixer but it can be done by hand using a whisk and spatula instead).

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).

Drizzle in milk while stirring and stir until batter is uniform and completely combined.

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. Scrape the sides and bottom of the bowl to ensure everything is well-combined. The batter will be very thin, this is normal!

Evenly divide batter into prepared muffin tin, but take care to fill 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. Over-filled liners will result in cupcakes with flat tops and they may cave in on themselves. If you have excess batter, discard it (or make extra cupcakes!).

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 (I like to use a knife to gently pry up the cupcake from the bottom and then carefully lift it out to a cooling rack). Repeat with second pan of cupcakes

Once cupcakes have cooled, frost with my chocolate frosting or your favorite frosting recipe.