Step 1

Preheat the oven to 350°F (180°C) and line two baking sheets with parchment paper. In a medium bowl, whisk together the flour, cocoa powder, black cocoa, baking powder, and salt until combined, then set aside.

Step 2

Place the butter and chopped chocolate in a heatproof bowl and set over a pan of gently simmering water to create a double boiler. Stir occasionally until the chocolate is fully melted. Then remove the bowl from the heat and set aside.

Step 3

In the bowl of a stand mixer fitted with the whisk attachment or in a large bowl using an electric hand mixer, whisk together the eggs, sugars, and vanilla for 5-6 minutes on medium-high speed.

Step 4

With the mixer on, pour in the slightly cooled chocolate mixture and mix until smooth. Sift in the dry ingredients and use a rubber spatula to gently fold until just combined.

Step 5

Using a 3-tbsp cookie scoop, drop 6 cookies on each prepared pan. Make sure to leave plenty of space between each cookie as they will spread when they bake.

Step 6

Sprinkle each cookie with a little flaky sea salt and then bake one tray at a time for 12-13 minutes. The cookies will be soft so allow them to cool on the baking trays for at least 15 minutes before removing from the tray to cool completely.