Position a rack in the center of the oven and preheat to 350 degrees F. Line
a 13 x 9-inch pan with aluminum foil so that the foil extends 2 inches beyond the
two long sides of the pan. Butter the bottom and sides of the foil-lined pan.
Brownie: In a medium saucepan, combine butter and sugars. Cook over medium heat, stirring
constantly with a wooden spoon until the butter is melted and the mixture is very
Place the chocolate chips and unsweetened chocolate in a food processor fitted
with the metal chopping blade. Process the chocolates for 15 to 20 seconds or until
With the motor running, pour the hot butter mixture through the
feed tube and process for 15 to 20 seconds or until the chocolate is completely
melted, scraping down the work bowl as necessary.
Add the eggs and vanilla extract
and process for 10 to 15 seconds, or until combined.
Add the flour, espresso powder
and salt and process for 5 to 7 seconds, just until combined, scraping down the
work bowl as necessary.
Add the walnut halves and pulse about 10 times to incorporate
them into the mixture and to chop them slightly.
Scrape the batter into the prepared pan and smoother the top with a rubber spatula.
Bake the brownies for 25 to 30 minutes or until a cake tester or wooden pick inserted
2 inches away from the center comes out with a few moist crumbs clinging to it.
Do not over-bake the brownies.
Cool the brownies completely in the pan set on a wire rack.
Using the two ends
of the foil as handles, lift the brownies out of the pan. Invert onto a cutting
board and peel off the aluminum foil. Re-invert the brownies so they are top side
up. Using a sharp knife, trim the sides of the brownies so that they are straight
and smooth. Place the brownies on a wire rack and set the wire rack over a baking
Bittersweet Chocolate Glaze: Do not make the glaze until the brownies are cool.
In a medium saucepan over medium-low heat, bring the cream to a gentle boil. Take
the pan off the heat and add the chocolate. Let the mixture stand for 30 seconds
to melt the chocolate.
Using a wire whisk, stir until the mixture is smooth.
Strain the glaze through a fine sieve into a small bowl to remove any air bubbles.
Cool the glaze for 5 minutes, or until slightly thickened but still pourable.
Pour the glaze evenly over the brownies, allowing the glaze to drip down the
sides onto the baking sheet. Spread the glaze with a small metal offset cake spatula,
making sure that the top and sides of the brownies are completely covered.