In a large bowl, cream the butter, brown sugar, and 2 cups sugar. Add eggs, vanilla, baking soda, unsweetened chocolate and salt. Add flour, mixing carefully and thoroughly. Place in a freezer ziploc bag and refrigerate for 2 hours.
Take dough out of freezer. Place 1/4 cup sugar in a small bowl. Roll dough into little balls and roll into sugar. Place in greased cookie sheets and bake for 350 degrees F. for 8-12 minutes.
Variation: Instead of unsweetened baking chocolate, use 3 tablespoons unsweetened baking cocoa and 1 tablespoon oil for each ounce on unsweetened baking chocolate.