6 tablespoons all-purpose flour
1/2 teaspoon baking powder
1/2 teaspoon salt
10 ounces semisweet chocolate, chopped into 1/4-inch pieces
2 ounces unsweetened chocolate, chopped into 1/4-inch pieces
6 tablespoons unsalted butter
2 large eggs
1/2 cup granulated sugar
2 teaspoons pure vanilla extract
Heat the oven to 325 degrees F.
In a sifter combine the flour, baking powder and salt. Sift onto a large piece of wax paper and set aside until needed.
Heat 1 inch of water in the bottom half of a double boiler over medium heat. With the heat on, place 6 ounces semisweet chocolate, the unsweetened chocolate, and butter in the top half of the double boiler. Use a rubber spatula to stir the chocolate and butter until completely melted and smooth, about 6 minutes. Transfer the melted chocolate mixture to a 1-quart bowl and set aside until needed.
Place the eggs, sugar and vanilla extract in the bowl of an electric mixer fitted with a paddle. Beat on medium 4 minutes until soft. Use a rubber spatula to scrape down the sides of the bowl, then continue to beat on medium for 2 more minutes. Stop the mixer, then add the melted chocolate and beat on medium for 1 minute until incorporated. Scrape down the bowl. Add the sifted dry ingredients and the remaining 4 ounces semisweet chocolate and mix on low speed until just incorporated, about 30 seconds. Remove the bowl from the mixer and use a rubber spatula to finish mixing the dough until thoroughly combined.
Using a heaping tablespoon of dough for each cookie (approximately 3/4 ounce), place 12 cookies, evenly spaced, onto each of 3 nonstick baking sheets. Place the baking sheets on the top and center racks of the preheated oven and bake for 9 to 10 minutes, rotating the sheets from top to center about halfway through the baking time (at this time also turn each sheet 180 degrees).
Remove the cookies from the oven and allow to cool to room temperature on the baking sheets, about 30 minutes. Store the cooled cookies in a tightly sealed plastic container until ready to serve.
Yields 3 dozen.