I found this recipe at Recipe.com and it's from Better Homes & Gardens. I was afraid the cookie would be hard by looking at the photo. I baked them for 7 minutes and they are soft and a little fragile. I am too impatient to wait the one hour before spreading the filling and I'm glad I didn't wait. It was much easier to spread when it was warm. I adore sandwich cookies and these turned out great. Chocolate & mint!
Minty Cocoa Fudge Sandwich Cookies
3 1/2 c. flour
2/3 c. unsweetened cocoa powder
2 t. baking powder
1 1/3 c. butter, softened
1 1/2 c. sugar
1/4 c. canola oil
1 T. vanilla
1 (14-oz.) can sweetened condensed milk
1 (10-oz.) package mint-flavor semisweet chocolate pieces*
2 oz. unsweetened chocolate, coarsely chopped
In a medium bowl, combine flour, cocoa powder, and baking powder; set aside.
In a large bowl, beat butter with an electric mixer on medium to high speed for 30 seconds. Add the 1-1/2 cups sugar and the oil. Beat until well mixed. Add eggs and vanilla; beat until combined. Add flour mixture; beat until combined. Cover and chill about 1 hour or until dough is easy to handle.
Preheat oven to 350º. Shape dough into 1-inch balls. Place balls 2 inches apart on an ungreased cookie sheet. Dip the bottom of a glass in additional sugar and flatten each cookie. Bake in preheated oven for 7 to 9 minutes or just until firm. Transfer cookies to a wire rack; let cool.
For filling: In a small saucepan, combine sweetened condensed milk, chocolate pieces, and unsweetened chocolate. Cook and stir over medium heat until melted and smooth. Remove from heat. Let stand about 1 hour or until cool.
Spoon a rounded measuring teaspoon of the filling on the bottom of each of half of the cookies. Top with remaining cookies, flat sides down, pressing lightly together. Makes about 36 sandwich cookies.
*If you can't find mint-flavor semisweet chocolate pieces, use 1 1/2 cups regular semisweet chocolate pieces and stir 1/4 teaspoon mint extract into the melted chocolate mixture.
To Store: Place filled cookies in a single layer in an airtight container; cover. Store at room temperature for up to 3 days or freeze for up to 3 months.