Preheat the oven to 350℉. Line two baking sheets with parchment paper.
Sift together the flour, cocoa powder, espresso powder, baking powder, and salt. Set them aside.
¾ cup+1tbsp All-purpose flour, 1 teaspoon Baking powder, ¼ teaspoon Salt, 2½ tablespoon Un- sweetened cocoa powder, ½ teaspoon Espresso powder
Prepare a double boiler, place the chopped chocolate and the butter in the top bowl and let the butter and chocolate melt. Once smooth, set aside to cool down.
½ cup+1tbsp Butter, 1¼ cup Semi-sweet chocolate
Set the stand mixer on the whisk attachment and beat the sugars, eggs, yolk, and vanilla extract at medium to high speed. Let the stand mixer go for a couple of minutes until the mixture is light in colour and creamy. This contributes to that beautiful cracked top.
½ cup Brown sugar, ½ cup Granulated sugar, 2 Eggs, 1 tablespoon Vanilla extract, 1 yolk
Lower the speed of the mixer, add the chocolate and butter mixer, and keep whisking until completely mixed.
Using a rubber spatula, mix in the dry ingredients and mix well. Put the bowl back on the mixer, and whisk for only 15 seconds. DO NOT OVERMIX.
Scoop the mixture on the prepared baking sheets. Sprinkle some salt flakes. Bake for 12 minutes. Bring out of the oven and let cool down for a few minutes, then transfer to the cooling rack.
1 tablespoon Salt flakes