From page 174-177 in Sticks & Scones , Diane Mott Davidson, New York: Bantam Books, c2001

Diane Mott Davidson's
911 Emergency Cookies

6 ounces semisweet chocolate chips
6 ounces bittersweet chocolate, broken into large pieces (recommended brands: Lindt Bittersweet, Godiva Dark)
1 stick unsalted butter, softened and divided
1-1/2 cups all-purpose flour
1/3 cup unsweetened Dutch-style cocoa (recommended brand: Hershey’s European-style)
1-1/2 teaspoons baking powder
1/2 teaspoon salt
3/4 cup dark brown sugar, firmly packed
3/4 cup granulated sugar
3 large eggs
1 1/2 teaspoons vanilla extract
Vanilla Icing (recipe follows)

In the top of a double boiler, melt the chips, chopped chocolate, and 4 tablespoons (1/2 stick) of the butter. When melted, set aside to cool briefly.

Sift together the flour, cocoa, baking powder, and the salt. Set aside.

In a large mixing bowl, beat the remaining 4 tablespoons of butter with the sugars. When the mixture is the consistency of wet sand, add the eggs and vanilla. Mix in the slightly cooled chocolate mixture, beating only until combined. Stir in the flour mixture, mixing only until completely combined and no traces of flour appear.

Cover the bowl with plastic wrap and refrigerate for 25 minutes, until the mixture can be easily spooned up with an ice-cream scoop.

Preheat the oven to 350°F. Butter two cookie sheets.

Using a 4-teaspoon ice-cream scoop, measure out a dozen cookies per sheet. Bake one sheet at a time for about 9 to 11 minutes, just until the cookies have puffed and flattened. Do not overbake; the cookies will firm up upon cooling. Allow the cookies to cool 2 minutes on the cookie sheet, then transfer them to the racks and allow to cool completely.

Frost with Vanilla Icing.

Makes 4 dozen cookies.

Vanilla Icing-

4 tablespoons (1/2 stick) unsalted butter, softened
1/3 cup whipping cream
3/4 teaspoon vanilla extract
2-3/4 cup confectioners’ sugar, or more if needed.

Beat the butter until very creamy. Gradually add the cream, vanilla, and confectioners’ sugar and beat well. If necessary, add more confectioners’ sugar to the icing. It should be fairly stiff, not soupy. Spread a thick layer of icing on each cookie.