Preheat oven to 350 degrees F. Cream butter and brown sugar with electric mixer at medium speed until fluffy. Beat in egg and vanilla. In a separate bowl, combine flour, baking powder, and salt. Add flour mixture to batter slowly. Blend thoroughly. Turn out dough on surface and knead until smooth. Refrigerate for 2-3 hours. Let dough sit out for a few minutes to soften slightly. Roll into golf-ball sized balls and press with cookie presses on baking sheet. Bake 10-12 minutes. Cool on rack. Decorate as desired or enjoy as-is.