In a large mixing bowl, cream together butter & sugar until light & fluffy, about 2-3 minutes.
Add in egg & vanilla extract & mix until combined.
In a separate bowl, combine flour, baking powder, and salt.
Slowly add the flour mixture to the butter mixture in 3 increments, mixing until mostly combined before adding more flour. Do NOT overmix.
Roll the dough between 2 sheets of parchment paper to ¼" thick & place on a baking sheet in the refrigerator.
Chill for about 20-30 minutes.
Cut dough into shapes with cookie cutters and transfer to a baking sheet.
Bake at 350° for 8-10 minutes. You do NOT want them to brown. They should look puffy & barely cooked, they will continue to cook when they're on the baking sheet.
Cool on baking sheet 5 minutes, then transfer to a baking rack (preferred) or plate to cool completely.
