In a large bowl, cream butter and sugar until light and fluffy. Beat in eggs and vanilla. Combine the flour, baking powder and salt; gradually add to creamed mixture and mix well. Refrigerate for 1 hour or until firm. On a lightly floured surface, roll out dough to 1/4-inch thickness. Cut out with Christmas cookie cutters of your choice. Using a floured spatula, transfer cookies to greased baking sheets. Bake at 375° for 8-10 minutes or until lightly browned. Cool completely on wire racks. Decorate cookies with frosting, sugars and candies. Yield: 6-7 dozen (2 1/2-inch cookies).