2 1/2 sticks unsalted butter, plus more, softened, for greasing
8oz semisweet chocolate chips
3/4cup unsweetened dutch process cocoa powder, divided
1 tsp instant coffee
1 1/2cups granulated sugar
1/2cup dark brown sugar, packed
2 teaspoons vanilla extract
2 teaspoons kosher salt
1cup egg whites (or 6 large egg whites)
1cup all-purpose flour
flaky sea salt, for sprinkling (optional)
Instructions
Heat the oven to 350 degrees. Grease a 9×13 baking dish, place parchment paper inside, and then spray the parchment paper. Place the chocolate chips, instant coffee, and 1/4 of the cocoa powder in a small mixing bowl. Melt the butter, pour the batter on top of the chocolate mixture, whisk until melted, and then set aside to cool slightly.
In a standing mixer, combine the sugar, brown sugar, and egg whites and beat until very fluffy, about 4-5 minutes, lower the speed, add the vanilla, and slowly pour in the melted chocolate mixture. Turn off the mixer.
Sift the flour and the rest of the cocoa powder (1/2 cup) and gently fold into the wet ingredients until combined. Pour into the baking dish and bake for 20 minutes. Turn off the heat and allow the brownies to sit in the oven for an extra 5 minutes, then remove and cool before cutting into squares.