The recipe is from “A Country Baking Treasury by Lisa Yockelson” via Carol Ramos
1 Cup (2 sticks) unsalted butter, cut into rough chunks
4 Tbsp. unsifted unsweetened cocoa powder
1 Cup water
2 Cups granulated sugar
2 Cups unsifted cake flour
1 tsp. salt
1/2 Cup buttermilk, blended with 1 teaspoon baking soda, at room temperature
2 extra-large eggs at room temperature
1 1/2 tsp. pure vanilla extract
Chocolate Fudge Frosting:
1/2 cup (1 stick) unsalted butter, cut into chunks
2 ounces unsweetened chocolate, chopped
5 tablespoons milk, at room temperature
1 tablespoon light cream, at room temperature
1 box (1 pound) confectioners’ sugar, sifted
1 teaspoon pure vanilla extract
Pinch of salt
1 cup chopped pecans
Lightly butter and flour a 9 x 13 x 2-inch cake pan; set aside. Preheat the oven to 400˚F.
For the cake, place the butter, cocoa, and water in a large saucepan, set over moderately high heat, and bring to a boil.
Remove from the heat. Sift together the sugar, flour and salt into the large bowl of an electric mixer.
Whisk together the buttermilk, eggs and vanilla in a mixing bowl. Pour the hot butter-cocoa-water mixture over the sifted dry mixture and beat on moderate speed until thoroughly blended.
Add the whisked egg mixture and continue beating on low speed until the batter is a uniform color, about 1 ½ minutes. Pour and scrape the batter into the prepared pan.
Bake the cake on the lower-third-level rack of the preheated oven for 20 to 22 minutes, or until a wooden pick inserted into the center of the cake comes out clean and dry and the cake shrinks slightly away from the edges of the pan.
About 10 minutes before the cake is done, make the fudge frosting. Place the butter, chocolate, milk and cream in a large saucepan, set over low heat and cook, stirring occasionally, until the chocolate has melted down completely.
Remove from the heat and beat in the sugar by cupfuls with the vanilla and salt. Blend in the pecans.
As soon as the cake is done, remove it from the oven to a wire cooling rack. Immediately spread the frosting evenly over the top with a flexible palette knife. Let the cake cool in the pan.
For serving, cut the cake in squares directly from the cake pan.