Prepare masa (see recipe link above). You can also use Masa Instantanza if you wish. Prepare according to the package directions.
In a large bowl, combine the masa, brown sugar, and vanilla until well blended.
To assemble the tamales, place 1/2 cup of the masa in the center of the smooth side of a corn husk. Using the back of a wet tablespoon, make an indentation in the center of the masa and fill with 1 1/2 tablespoons or more of the chocolate chips. Fold both sides of the husk tightly in over the masa mixture and tie a t both ends. Repeat for the reaming tamales. Steam the tamales for 55 minutes. Serve plain or with whipping cream.