In a bowl, sift together first four ingredients. Set aside.
In large bowl, cream butter and shortening on medium speed until light and fluffy. Add confectioners sugar and beat on low speed until smooth. add egg and vanilla extract and beat on low until well combined.
On low speed, slowly add dry ingredients. Beat until well combined. Cover with plastic wrap. Refrigerate until very firm and cool, at least 2 hours.
Preheat oven to 350. Take some of the dough and shape it into 1-inch balls. (Keep remaining dough in the refrigerator, as it must be kept chilled.) Place balls on ungreased cookie sheet and press with the tines of a fork to flatten. Bake until golden, but not brown, 10 to 12 minutes. Cool slightly on the baking sheet on a rack. then using a spatula, transfer the cookies to a rack to cool completely.