In large bowl, stir together flour, baking powder and salt. In large bowl, beat butter and sugar with electric mixer until light and fluffy. Beat in egg and vanilla. Add flour mixture to butter, 1 cup at a time, mixing until just combined.
Roll cookie dough into 2 in. balls; press 3 Eggnog Candy Melts candy discs into the center of each ball, forming the dough around the candy. Place on cookie pan 2 in. apart; flatten slightly.
Bake 18-20 minutes or until edges of cookies are lightly browned. Cool on cookie pan 2 minutes; remove to cooling grid. If desired, drizzle tops with remaining candy.
Cookies are best served warm. Reheat in microwave for 30-45 seconds for gooey, just from the oven taste.