INGREDIENTS
1/2 cup
unsalted butter, softened
3/4 cup
dark brown sugar, packed (I have not tried using light brown sugar)
1
large egg
1 tbsp
vanilla extract
1 1/2 cups
all-purpose flour
1/2 cup
unsweetened natural dark cocoa powder (I used Hershey’s Special Dark; regular cocoa powder or Dutch-processed may be substituted)
1 tsp
cornstarch
3/4 tsp
baking soda
salt, optional and to taste