Press dough onto the bottom of an ungreased 13-in. x 9-in. baking pan (dough will be thin). Bake at 350° for 11-13 minutes or until edges begin to brown.
Immediately sprinkle with chocolate chips. Allow chips to soften for a few minutes, then spread over bars. Drop spoonfuls of melted vanilla chips over top; cut through chocolate with a knife to swirl. Let stand until set. Cut into bars.