1/4 cup buttermilk

1 cup powdered sugar

1 teaspoon vanilla

1 cup chopped walnuts

1. Preheat the oven to 400 F. Butter a 9-inch spring form pan. Combine the dry ingredients together and reserve.

2. In a medium (3 quart) non-stick saucepan, bring the water, butter, cocoa and espresso to a boil on medium-high heat, stirring for 2 minutes. When it comes to a boil add the dry ingredients, stirring to combine. Reduce the heat to medium. Then add the buttermilk, eggs and vanilla, and mix vigorously until well blended. Remove from the heat. (Do not cook too long or it will affect the rising of the cake.)

3. Pour into the prepared pan. Bake for about 15 minutes or until the top just begins to crack and the center is still slightly wet when pierced with a skewer.

4. Clean the saucepan, then while the cake is baking make the frosting. In the saucepan over medium-high heat bring the butter, cocoa and buttermilk to a boil, mixing constantly. When blended add the powdered sugar, vanilla and walnuts, and mix to combine. Remove from the heat.

5. While the cake is still hot, poke holes in the cake and pour over the frosting. Keep poking the cake after you have poured over the frosting to create a fudgy interior. When the cake is completely set, place it on a platter and release the spring form allowing the frosting to drip down the side. Serve warm or room temperature.

Recipe note: For a crowd, double the recipe and place in a 9-by-13-inch baking pan. Cut into squares and serve with ice cream.

Advance preparation: This may be prepared a day ahead, covered and kept at room temperature.

(Diane Rossen Worthington is an authority on new American cooking. She is the author of 18 cookbooks, including "Seriously Simple Parties," and a James Beard Award-winning radio show host. You can contact her at www.seriouslysimple.com.)