In a large bowl of stand mixer (or use a hand mixer instead) add 2 room-temperature 8oz blocks cream cheese, ½ cup sour cream, 1 large egg, and 3 additional egg yolks. (Discard whites or save for later.) Mix briefly, then scrape down the sides and bottom of the bowl.
Add ½ cup sugar, and 2 tsp vanilla, then mix thoroughly on high until smooth and creamy. (Note: if the cream cheese is cold, it will be blobby, not smooth.)
Pour the filling onto the sugar cookie crust and use a spatula or spoon to smooth the surface if needed.
Bake at 350°F for 40-45 minutes or until center is set and only barely jiggles. Allow to cool fully.