Preheat oven to 375 degrees.
Using a mixer, cream butter in a large bowl, beating until light and fluffy. Slowly add the sugar and brown sugar.
Add eggs one at a time, mixing after each, add vanilla and beat just until smooth. By hand, stir in flour, slat, and baking soda until well blended. Stir in the chocolate chips.
Rinse the Vidalia onions with very cold water and drain well. Fold the Visalia onions into the dough to blend. Drop by spoonfuls onto cookie sheet. Bake for 10-12 minutes or until lightly browned.