Place butter and sugar in the bowl of a stand mixer (you can also use a large bowl and a hand mixer). Beat on high until light and fluffy.
Add the eggs, sour cream, and vanilla. Beat to combine.
Stir in the flour, baking powder, baking soda, and salt. Chill the dough for at least 2 hours (or up to 48 hours).
Preheat oven to 400°F. Line a baking sheet with parchment paper or a silicone mat.
Use a cookie scoop to scoop 1½ inch balls onto the baking sheet. Keep 2 inches in between the balls of dough.
If you’re using sanding sugar, roll each ball in sanding sugar before placing on the baking sheet.
Bake for 9–10 minutes, or until the edges are golden brown. Let cool.
If you’re using frosting, place all frosting ingredients in the bowl of a stand mixer. Beat on high until light and fluffy (you can also use a bowl and a hand mixer).
Frost the cookies and top with sprinkles, if desired.
Notes
The edible gold stars in the photos above can be found on Amazon. The cookies can be stored for 4–5 days at room temperature. You can also freeze the cookies (leave the frosting off before freezing so the frosting will still look nice). Keep them in an even layer or place pieces of wax paper between layers. Defrost at room temperature. You can freeze balls of cookie dough to bake later. Use full-fat sour cream for best results.