Homemade Oreo Cookies

1 cup butter (no substitutes), softened
2 cups sugar
2 eggs
1 teaspoon vanilla extract
3 cups all-purpose flour
2/3 cup baking cocoa
1 teaspoon baking soda
1 teaspoon salt
1/2 cup milk
FILLING:
1/2 cup butter or margarine, softened
1 1/2 cups confectioners' sugar
1 cup marshmallow creme
1 teaspoon vanilla extract

In a mixing bowl, cream butter and sugar. Add eggs, one at a time, beating well after each addition. Beat in vanilla. Combine the flour, cocoa, baking soda and salt; add to creamed mixture alternately with milk. Refrigerate for at least 2 hours. Drop by rounded teaspoonfuls 2 in. apart onto greased baking sheets. Bake at 375 degrees F for 10-12 minutes or until edges are set. Remove to wire racks to cool.

Combine filling ingredients in a small mixing bowl; beat until smooth. Spread on the bottom half of the cookies; top with remaining cookies. Store in the refrigerator.