In a medium-size bowl, whisk together flour, baking powder and salt. Set aside.

In a large bowl, beat butter and sugar until smooth, about 2 minutes. Beat in egg and vanilla. On low speed, beat in flour mixture until just combined. Divide the dough in half and form each half into a disk. Wrap in plastic wrap and refrigerate 4 hours or overnight.

Heat oven to 350 degrees F. On a lightly floured surface, roll out one disk to 1/4-inch thickness. Cut into bells using a 2-inch bell-shaped cookie cutter. Place on an ungreased baking sheet. Sprinkle with white nonpareils, gently pressing to adhere. Bake for 10 to 12 minutes until lightly golden around edges. Remove cookies to wire racks to cool completely.

Repeat with remaining half of dough. Gather scraps and refrigerate. Reroll and cut into additional bells. Bake and cool as above. When completely cool, cookies may be stored in an airtight container up to 2 weeks.