Add the flour, cocoa powder, baking soda, baking powder, cornstarch, salt and sugar to a bowl, stir to combine. Add the eggs, vanilla, sour cream, vegetable oil, beer, and chocolate chips. Stir to combine.
Pour into an 8 ½ x 4 ½ inch loaf pan.
Bake until the top has puffed and is hard, about 40-50 minutes.
Remove from oven, allow to cool to room temperature. Cut into slices to serve.