Fudgy Dense Brownies

Preheat oven to 350°F.

Lightly grease an 8 × 8-inch metal baking pan.

Line the pan with parchment paper, leaving enough overhang on two sides to lift the brownies out after cooling.

Add butter and the 6 ounces chopped chocolate to a heatproof bowl.

Melt together gently using a double boiler or microwave in short 20-second intervals, stirring between each interval.

Stop heating as soon as the mixture is completely smooth.

Set aside for approximately 5 minutes so it remains warm but is no longer extremely hot.

In a separate large bowl, combine the dark brown sugar and granulated sugar.

Add the 2 whole eggs and 1 egg yolk.

Whisk vigorously for approximately 1–2 minutes until the mixture looks smoother, slightly lighter, and glossy. Do NOT whip until extremely airy. We want enough agitation to help create the shiny top without incorporating excessive air that could make the brownies cakey.

Whisk in vanilla.

Slowly pour the warm melted chocolate-butter mixture into the egg mixture while whisking.

Continue whisking until completely smooth, dark, and glossy.

In a separate bowl, whisk together: - flour - Dutch-process cocoa - salt - optional espresso powder

Sift the dry mixture over the chocolate mixture if the cocoa contains visible lumps.

Using a silicone spatula, gently fold the dry ingredients into the wet ingredients.

Stop folding as soon as only a few small streaks of flour remain.

Add the optional 4 ounces chopped chocolate.

Fold only until evenly distributed and no dry flour remains. DO NOT OVERMIX.

Transfer batter to the prepared 8 × 8-inch pan.

Spread evenly into the corners.

Smooth the surface.

Sprinkle very lightly with optional flaky sea salt.

Bake on the center rack for approximately 27–32 minutes.