Heat treat your flour by microwaving it in a bowl for around 1 -2 minutes or until it's hot, or pouring it on a baking sheet and baking it in a preheated oven (350°F) for 5 minutes, then set aside to cool* (SEE NOTES)
In a medium microwave-safe bowl, melt butter. Whisk in the sugars until the mixture is combined. Add in the vanilla extract. Add in the flour, cocoa powder, and salt and mix. Mix in the 3 tablespoon milk, then add more 1 tablespoon at a time until your desired consistency is reached.
Stir in the chopped chocolate or chocolate chips or other toppings and enjoy!