Pre-heat the oven to 350F and line a 8x8 metal baking pan with parchment paper. Spray the paper with cooking spray.
Whisk the melted butter and the Swerve together in a large mixing bowl until smooth. Add eggs and vanilla and beat with an electric mixer for 1 minute.
Add in the melted bakers chocolate and stir until just combined. With a rubber spatula, add in the coconut flour, cocoa powder, baking powder, salt, and stir until just combined. Fold in the chocolate chips or walnuts if using.
Pour the batter into the prepared pan and smooth out the top with a spatula.
Bake in the oven for 30 minutes. Remove from the oven and let cool in the pan for 30 minutes. Remove from the pan and cut into 9 squares. Store in an airtight container.