In a large bowl with electric mixer, beat butter, shortening, sugar baking soda and salt. Beat in egg and vanilla until pale and fluffy. Stir in flour just until blended. Wrap in plastic wrap and chill at least 30 minutes. Heat oven to 350 degrees F Divide dough in half. Rewrap half and refrigerate until needed. Roll out on lightly floured surface to 1/4 inch thickness. Cut with a cookie cutter of any design and put cookies on an ungreased cookie sheet about 2 linchs apart. Bake 9 to 10 minuted, until bottoms are light brown. Remove to wire rack to cool
