Preheat oven to 180°C (350°F) and fold a 15 cm x 15 cm (7 inch x 7 inch) brownie pan with parchment paper.
Cut the dark chocolate into chunks and transfer to a microwave-safe bowl with coconut oil or butter; place in the microwave and cook until completely melted. This should take about 1 minute and 30 seconds to 2 minutes. As an alternative you can melt using the Bain-Marie method.
In a large mixing bowl, combine granular sweetener with almond flour, cocoa powder, baking powder, vanilla extract and salt.
Add the melted chocolate mixture to the bowl. Using a fork or spatula, stir to combine into a brownie batter.
Add one egg at a time, whisking well after each one until completely incorporated in the keto brownie batter.
Transfer the brownie batter to the prepared baking pan and top with sugar-free chocolate chips if you desire.
Bake in hot oven for 15 to 20 minutes - bake for less time if you want a fudgy texture or bake for longer for cake-y brownies.