Preheat the oven to 350°F. Line an 8 x 8–inch baking dish with parchment paper, securing it with metal binder clips on two sides for stability.
In a medium-sized saucepan, melt the chocolate and butter until smooth. Stir in the cocoa powder and allow the mixture to cool. Set aside.
In an electric stand mixer with the whisk attachment, beat eggs, sugar, and vanilla on medium-high for 5 to 7 minutes until the mixture lightens in color and doubles in volume.
With the mixer on low, add the melted chocolate (no need to let it completely cool) and run the mixer for 30 seconds on low to combine.
Using a rubber spatula, gently fold in the flour and 1 teaspoon of sea salt until just combined. Avoid overmixing.
Pour the batter into the prepared baking dish. If desired, sprinkle sea salt flakes on top.
Bake in the middle of the oven for 20-25 minutes. The tops should have a nice shine, and a toothpick inserted should come out with a few moist crumbs.
Allow the brownies to cool completely in the pan for about 20-30 minutes to set up.
Cut into 9 or 16 squares and enjoy your delicious Crinkle Top Brownies!