In a separate bowl whisk together flour and baking powder.
Beat together unsalted butter and sugar. Once mixed well, add in egg. Mix again, then add in vanilla. I like to use my Kitchen aid and dough hook.
Slowly add in flour mixture about a cup at a time. Mix until dough forms and begins to clump together.
Gather up dough and knead it with hands until its nice and smooth. Roll it into a ball, wrap with plastic wrap, and place in fridge to chill. I like to let min chill about 20-40 minutes. You will want it to be kind of firm but not hard. If its too hard...just leave it out on the counter for just a little bit until it softens up. Then you can work it a little bit to soften it back up.
Bake at 350, time will depend on cookies size and thickness. Normally between 7-11 minutes.