Grease and flour a 13x9x2-inch baking pan; set aside. In a large mixing bowl stir together flour, sugar, cocoa powder, baking soda and salt. Stir in water, oil, vinegar and vanilla. Beat mixture with a fork until smooth. Pour into prepared pan. Sprinkle with Picnic Topping.

Bake in a 350 degree F oven for 30 to 40 minutes or until a wooden toothpick inserted near the center comes out clean. Cool cake slightly in pan on a wire rack. Serve warm with a scoop of vanilla ice cream and drizzle with Grandma Betty's Chocolate Sauce. Makes 12 servings.

Picnic Topping: In a bowl, combine 1 cup chopped walnuts, 1 cup semisweet chocolate pieces and 1/2 cup sugar. Sprinkle topping to cover cake batter.

Grandma Betty's Chocolate Sauce: In heavy small saucepan, combine 1-1/2 cups sugar, 3 tablespoons unsweetened cocoa powder and a dash of salt. Stir in 1/2 cup whipping cream and 1/4 cup milk. Bring to a gentle boil, stirring constantly, then reduce heat. Cook and stir for 2 minutes. Remover from heat. Stir in 1 teaspoon vanilla. Transfer to bowl; cover surface with plastic wrap. Cool to room temperature before using.