Beat butter, shortening and brown sugar until creamy. Beat in baking powder, salt, vanilla and egg. Stir in flours. Divide dough in half. Cover and refrigerate about 2 hours.
Heat oven to 375°F. Roll each half of dough into 15x6-inch rectangle on floured surface. Cut lengthwise into three 15x2-inch strips, then cut crosswise into two 7 1/2x2-inch strips. Working quickly, spread about 1 teaspoon melted chocolate over one strip to within 1/4 inch of one long side. Gently roll up, starting at long side with chocolate. Repeat with remaining cookie strips and chocolate. Cut each roll into 2 pieces; roll each cookie slightly to shape. On ungreased cookie sheet, place cookies about 1 inch apart.
Bake 8 to 10 minutes or until edges are firm. Cool 1 minute; remove to cooling rack. Cool completely. Place remaining chocolate in plastic bag. Cut hole in corner and squeeze out chocolate to look like ties.