Preheat the oven to 175 degrees Celsius (fan-forced). Line two baking trays with baking paper and set aside.
Place the butter and dark chocolate into a small microwave-safe bowl. Melt in the microwave on 50% power in 30 second bursts until just melted. Set aside.If using a Thermomix: Melt the butter and chocolate for 3-5 minutes, 50 degrees, Speed 2. Scrape down the sides and mix for an extra 10-20 seconds if needed. Set aside in a separate bowl.
In a large mixing bowl, use hand-held beaters or a stand-mixer to beat the eggs, caster sugar, brown sugar and vanilla extract for 3 minutes or until doubled in size. If using a Thermomix: In a clean and dry Thermomix bowl, insert the Butterfly attachment. Beat for 3-5 minutes, Speed 3.5, at 37 degrees. Remove the Butterfly.
Add the melted chocolate mixture and beat through. If using a Thermomix: Add the melted chocolate mixture and mix for 20 seconds, Speed 3. Scrape down the sides of the bowl and mix for a further 10 seconds or until combined.
Sift over the plain flour, cocoa powder, baking powder and a pinch of salt. Fold through with a spatula. If using a Thermomix: Add the flour, cocoa powder, baking powder and a pinch of salt. Mix for 5 seconds, Speed 5. Scrape down the sides of the bowl and repeat for a further 5 seconds.
Note: at this stage the batter will be VERY liquidy! This is fine! Place heaped tablespoons of the mixture onto the prepared baking trays - allowing room for the cookies to spread.
Bake for 10-12 minutes or until the cookies are very crackly. Remove from the oven and sprinkle with sea salt flakes. Allow to cool on the baking trays for 5 minutes before transferring to a wire rack to cool completely.
Notes
RECIPE NOTES & TIPS
Use a good quality dark chocolate for maximum flavour - cheap cooking chocolate can taste waxy and dull.
Don’t overmix once the dry ingredients go in - just fold until combined.
The batter will seem runny, but don’t worry - it’s meant to be.
They’re ready when the tops are shiny and cracked but still slightly soft in the centre. They will firm up as they cool.
If possible, bake one tray at a time if you can - this helps keep the heat even for perfect crinkles.
Sprinkle the sea salt as soon as the cookies come out of the oven so it sticks nicely.
Store in an airtight container at room temperature for up to 4 days.
To freeze, place cooled cookies in a ziplock bag with baking paper between layers. Freeze for up to 3 months.
Thaw at room temperature, or pop in a warm oven for a few minutes to refresh.