Preheat oven to 325 F. Line a rimmed baking sheet with parchment paper or a silicone baking mat. Set aside.
In a medium saucepan (or in the microwave), melt the butter over low heat. Once the butter is fully melted, add the chocolate chips to the saucepan. Stir continuously until the chocolate chips have fully melted and the mixture is smooth.
Remove the saucepan from the heat. Stir in the cocoa powder until fully incorporated into the melted chocolate mixture.
In a separate mixing bowl, whip the egg whites using an electric mixer or whisk until they become frothy. Add the vanilla extract and granulated sugar, and continue to whip for an additional minute.
Slowly pour the melted chocolate mixture into the bowl with the egg whites. Mix on a low setting for about 30 seconds, ensuring the mixture is well combined.
Gently fold in the all-purpose flour, baking soda, and pinch of salt until just combined. Do not overmix.
Using a spatula or the back of a spoon, spread the batter onto the prepared baking sheet. Aim for a uniform thinness of no more than 1/4 inch. Evenly sprinkle the flaky sea salt over the top of the batter.
Place the baking sheet in the preheated oven and bake for approximately 15 minutes. Keep an eye on them, as thinner parts might cook faster.
Turn off the oven and let brittle cool in oven. Once cooled, break into pieces or cut into desired shapes and enjoy!