Preheat oven to 350°. Grease two large cookie sheets and set aside. In a large bowl, beat the egg and vegetable oil. Gradually add the sugar and continue beating until pale yellow in color. In another bowl, sift together the flour, COCOA, baking soda and salt. In a measuring cup, combine the buttermilk and VANILLA. While mixing, alternate adding the dry ingredients and buttermilk to the egg and sugar, beginning and ending with the dry ingredients. Drop the batter by tablespoons onto the cookie sheets. These will spread a lot, so make 6 cookies per sheet at a time. Bake 8-10 minutes, until the top springs back when lightly touched. Remove to wire racks to cool. When cool, spread filling between two cookies to make sandwiches.
For the filling, in a medium bowl, combine all of the ingredients and beat until light and fluffy.
Prep. time: 30 minutes
Baking time: 8-10 minutes per batch
Servings 12; Serving Size 1 sandwich cookie (95g); Calories 350; Calories from fat 140; Total fat 15g; Cholesterol 35mg; Sodium 240mg; Carbohydrate 52g; Dietary Fiber 2g.