Chocolate Espresso Cookies

6 ounces unsweetened chocolate

1 pound bittersweet chocolate

6 tablespoons butter

5 eggs

2 cups sugar

2 tablespoons brewed espresso

1 teaspoon vanilla extract

3/4 cup cake flour

2 teaspoons baking powder

1 teaspoon salt

1 pound chocolate chips

1 cup walnuts

1/4 cup powdered sugar

1. Heat the oven to 375 degrees. Bring a small saucepan filled with a couple of inches of water to a simmer. In a heatproof bowl large enough to sit over the simmering water, melt the unsweetened and bittersweet chocolates and butter. Remove from heat and let cool to room temperature, 10 to 15 minutes.

2. In a stand mixer with the whisk attachment, whip the eggs, gradually adding the sugar and continue to whip until soft peaks form. Add the espresso and vanilla extract to the egg mixture and mix to combine. Fold the egg mixture into the chocolate mixture.

3. Sift together the flour, baking powder and salt, then fold into the chocolate mixture. Mix in the chocolate chips and walnuts. Let the cookie dough rest at room temperature for 1 hour, or until it sets up. Scoop the cookie dough with a half-ounce ice cream scooper onto two parchment-lined baking sheets. Sprinkle the cookies with powdered sugar.

4. Bake the cookies until they begin to crack on top, 12 to 15 minutes. Cool on a wire rack.