Oh Happy Day

Celebrate the 15th birthday of Martha Stewart Living today by baking some chocolate brownies. (From scratch, please, no packet jobs.) Here's the recipe from Martha's book Desserts (Clarkson Potter):
1 cup coarsely chopped walnuts (optional)
I cup (2 sticks) unsalted butter plus more for pan
8 ounces best quality unsweetened chocolate such as Callebaut
5 large eggs
3 1/2 cups sugar
2 teaspoon instant espresso
1 tablespoon pure vanilla extract1 2/3 cups sifted all-purpose flour
1/2 teaspoon salt
1/2 cup semisweet chocolate chips.
Heat oven to 350 degrees. Spread the chopped walnuts on baking pan; toast until fragrant, 5-10 minutes. Transfer nuts to bowl to cool. Increase oven temperature to 400 degrees. Generously butter a 9-by-13 inch baking pan; set aside. Combine the chocolate and butter in a heat-proof bowl or on top of a double boiler. Set over a pan of simmering water until the chocolate mixture has melted. Remove from heat; set aside. In the bowl of an electric mixer fitted with a paddle attachment, beat the eggs, sugar, and espresso at high speed, 10 minutes. Reduce speed to low, and add the melted chocolate mixture and the vanilla; beat until combined. Slowly add the flour and salt; beat until just incorporated. Fold in the chocolate chips and toasted walnuts. Pour the batter into the prepared pan. Bake until the edges are dry but the center is still soft, about 35 minutes. Remove pan from oven, and transfer to wire rack to cool. Cut into 3-inch squares, and store in an airtight container up to 2 days.