Preheat oven to 375°F.
Cream butter and sugar in large mixing bowl until light and fluffy. Beat in eggs and vanilla. Combine flour, baking powder and salt. Gradually add to butter mixture; mix well. Divide dough in fourths.
Roll out one-fourth of dough at a time on lightly floured surface to 1/8-inch thickness. Keep remaining dough refrigerated. Cut into desired shapes with floured cookie cutters. Place 1 inch apart on unbuttered cookie sheets.
Bake 6 to 8 minutes or until lightly browned. Transfer cookies to wire racks; cool completely.
Decorate as desired. Store in cool place in airtight metal containers up to 1 month. Freeze up to 3 months.
Cream butter and salt together; add sugar and stir briskly. Stir in cream or milk and beat well. Add additional sugar or milk if necessary for spreading consistency. Makes 1 cup icing.