Combine first 8 ingredients in large bowl. Add molasses, shortening, and egg. Using electric mixer, beat until well blended. Beat in 1/2 cup boiling water. Chill dough 1 hour.
Preheat oven to 400°F. Roll chilled dough by generous tablespoonfuls into balls. Roll in additional sugar to coat. Place dough balls 2 inches apart on ungreased baking sheets. Bake until cookies are puffed and cracked on top and tester inserted into center comes out with some moist crumbs attached, about 12 minutes (do not overbake). Transfer cookies to racks and cool.