Line a small lamington tray or a square baking dish with baking paper.
Add the butter and chocolate melts to a saucepan and slowly melt. Stir often to combine and to make sure it doesn't burn.
When melted and combined, pour into a large bowl.
Slowly mix in the sugar, salt and vanilla.
Gently add the cocoa powder and mix.
Add the eggs and mix to combine.
Add the sourdough starter discard and gently stir until combined.
Pour the batter into the prepared tray and bake for about 30-40 minutes or until a skewer insterted into the centre comes out clean. It is a good idea to start checking from around the 25 minute mark.
Nutritional information is an estimate and provided as a courtesy. The values may vary according to the ingredients and tools that are used. Please use your preferred nutritional calculator for more detailed information.