Chocolate Sandwich Cookies

2 packages (18-1/4 ounces each) devil's food cake mix
1 cup vegetable oil
4 eggs

Filling:
1 package (8 ounces) cream cheese, softened
1/4 cup butter, softened
2-1/2 cups confectioners' sugar
1 teaspoon vanilla extract

In a large bowl, combine the cake mixes, oil and eggs until well blended. Roll into 1-in. balls. Place 2 in. apart on ungreased baking sheets. Do not flatten.

Bake at 350° for 8-10 minutes or until set. Cool for 5 minutes before removing to wire racks (cookies will flatten as they cool).

In a small bowl, beat cream cheese and butter until fluffy. Beat in sugar and vanilla until smooth. Spread on the bottom of half of the cookies; top with remaining cookies. Store in the refrigerator. Makes about 6 dozen.