Minty Cocoa Fudge Sandwich Cookies

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 speed for 30 seconds. Add the 1-1/2 cups sugar and the oil. Beat until combined. Beat in eggs and vanilla until combined. Beat in flour mixture. Cover and chill about 1 hour or until dough is easy to handle.

Preheat oven to 350 degrees F. Shape dough into 1-inch balls. Place balls 2 inches apart on an ungreased cookie sheet. Flatten cookies with the bottom of a glass dipped in additional sugar. Bake 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 chopped chocolate. Cook and stir over medium heat until chocolate melts; cool.

Spread filling on bottoms of half of the cookies, using 1 rounded teaspoon per cookie. Top with remaining cookies, bottom sides down, pressing lightly together.