Remove butter from the fridge 45 minutes before making the dough so it can soften just enough. Place in a stand mixer with the whisk attachment and add sugar; combine well. Add vanilla and egg; mix well.
In a separate bowl, whisk together flour and baking powder. Change out the whisk attachment to the hook attachment and add flour mixture to the butter mixture one cup at a time. Mix until dough reaches its doughy texture.
Place dough on the counter and roll into a ball. Cover with plastic wrap and place in the fridge for 30 minutes.
Preheat the oven to 350°.
Lightly dust the counter top with flour. Remove dough from the fridge and unwrap it. Place it on the floured counter top and roll it out until about a quarter inch thick, or to desired thickness.
Cover a cookie sheet with a piece of parchment paper. Using a heart cookie cutter, cut out each cookie and set on the cookie sheet. Once cookies are placed on the cookie sheet, put the cookie sheet in the freezer for about 2 minutes so cookie dough can become cold and cookies can hold their shape better.
Bake 7-8 minutes, or until the center of the cookies no longer have the undone look to them. (They will look darker in the center if they’re not done.) Allow cookies to sit on the cookie sheet and cool enough so they can easily be removed from the pan without breaking. Cool completely before frosting and decorating.