Preheat oven to 175c and line two baking sheets with parchment paper.

Place the chopped chocolate and butter in a bowl and melt. I usually do this in the microwave - in 30-second bursts or you can place it over a saucepan of gently simmering water. Once melted set aside to cool slightly.

Use an electric whisk to whisk together the eggs, sugars, and vanilla. They should be pale and roughly doubled in volume. Add in the melted chocolate. Stir to combine and then add the flour, salt, cocoa powder and baking powder

Stir in the chocolate chips.

Scoop the cookies onto the baking sheets leaving about 2 inches between each cookie.

Bake for 12 to 14 minutes until the tops are shiny and crackly. Remove from oven and sprinkle with flaky salt. Let cookies cool for 10 minutes on baking sheets, then transfer to a wire rack to cool completely.