Ingredients
2 sticks (1 cup) salted butter, plus more for the baking dish
1 1/3 cups granulated sugar
1/3 cup powdered sugar
4 ounces bittersweet chocolate, chopped
2 large eggs
1 tablespoon vanilla extract
1 cup all-purpose flour
1/3 cup cocoa powder
1 tablespoon instant espresso powder
Pinch kosher salt
8 ounces semisweet chocolate, chopped
Directions
Preheat the oven to 400 degrees F. Butter a 9-by-13-inch baking dish.
In a saucepan, melt the butter until just bubbling. Remove from the heat and whisk in the granulated sugar and powdered sugar until combined. Add the bittersweet chocolate and stir to melt. Add the eggs and vanilla, then mix until well combined.
Add the flour, cocoa powder, espresso powder and salt and fold in until well mixed.
Transfer to the prepared baking dish. Sprinkle the top with the chopped semisweet chocolate and bake until just set in the middle, 22 to 25 minutes.
Let cool completely, then cut in the pan into 16 pieces, or to your desired size.