In a medium bowl, whisk together the sifted flour, baking powder, baking soda, and salt. Set aside.

In the bowl of a stand mixer fitted with the paddle attachment, cream together the softened butter and granulated sugar on medium speed until light and fluffy, about 3-5 minutes. Scrape down the sides of the bowl as needed.

Add the eggs one at a time, beating well after each addition until fully incorporated. Mix in the sour cream and vanilla extract until just combined.

Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined. Be careful not to overmix the dough. The dough will be soft.

Divide the dough into two equal portions, flatten each into a disk, wrap tightly in plastic wrap, and refrigerate for at least 1-2 hours, or until firm enough to roll. This chilling step is crucial for easy handling.

Preheat your oven to 375°F (190°C). Line baking sheets with parchment paper.

On a lightly floured surface, roll out one disk of chilled dough to about 1/4 inch thickness. Use cookie cutters to cut out desired shapes, or simply use a round cutter or cut into squares. Gather scraps, re-roll, and cut more cookies.

Place the cut-out cookies about 1 inch apart on the prepared baking sheets.

Bake for 8-10 minutes, or until the edges are lightly golden and the centers are set. Do not overbake to keep them soft.

Remove from the oven and let cool on the baking sheets for 5 minutes before transferring to a wire rack to cool completely.

In a large bowl, using a stand mixer or electric hand mixer, beat the softened cream cheese and butter together on medium speed until smooth and creamy, with no lumps, about 2-3 minutes.

Gradually add the sifted powdered sugar, 1 cup at a time, beating on low speed until combined, then increasing to medium-high speed until fluffy. Add more powdered sugar for a thicker frosting, if desired.

Beat in the vanilla extract and pinch of salt until fully incorporated and the frosting is light and smooth.

Once the cookies are completely cool, spread or pipe a generous amount of cream cheese frosting on top of each cookie. Decorate with sprinkles if desired.