In the bowl of your stand mixer or in a large bowl using your hand mixer, mix the butter on medium speed until smooth and creamy.
Add the sugar and mix on medium-high until the mixture is light and fluffy.
Add the eggs one at a time, mixing on medium speed until well incorporated. Scrape down the sides of the bowl after each addition.
Add the sour cream and vanilla and mix on low speed until combined.
Add the flour, baking powder, baking soda and salt and mix on low speed until a soft dough forms.
Cover the bowl with plastic wrap and chill the dough for at least 2 hours. Ideally, overnight is best.
Preheat your oven to 350 degrees Fahrenheit after the dough has chilled sufficiently.
Scrape the dough out onto a well floured surface and roll it out until it's about 1/2 inch thick. Be sure to flour your surface well, along with your hands and your rolling pin to prevent sticking.
Flour a heart-shaped cookie cutter (or any shape you wish) and cut out the cookies, placing them on a parchment paper-lined baking sheet. This recipe makes about 3 dozen cookies, so repeat this rolling out process until all the cookies have been cut.
Bake at 350 degrees Fahrenheit for about 7-9 minutes, or just until the cookies lose their shine on top and appear slightly puffy.
Remove the cookies from the oven and let cool on the baking pans for about 5 minutes before transferring to a wire rack to cool completely.