1teaspoonvanilla(optional: will darken the frosting slightly)
In a large mixing bowl, beat butter and sugar together until light and creamy, about 3-4 minutes.
Add sour cream, egg and vanilla and beat until combined, scraping down the sides as necessary.
Add flour, baking powder and salt and mix until combined. A slightly soft dough should form.
Optional: you can chill this dough for 1 hour or overnight if you prefer, and it will be a little easier to work with. This isn't necessary though, and the cookies will still keep their shape even if baked right away.
Preheat oven to 350 degrees F.
Roll out cookie dough on a large piece of wax paper to ¼"-⅓" thickness (you can dust with a tiny bit of flour if necessary -- don't overdo it! If it is too sticky to roll, sprinkle a little flour on top -- the smallest amount possible). Cut out desired shapes and place on parchment-lined baking sheets.
Bake at 350 degrees F for 8-10 minutes, until they look slightly puffed and dry but are not yet browning at the edges. Don't overbake or they will become hard -- they may look slightly underdone in the center but will set up as they cool.
Let cool completely before frosting.
Sugar Cookie Frosting:
In a medium bowl, whisk together sugar, melted butter, milk and vanilla extract until smooth.
Spread over cooled cookies and decorate as desired. The frosting takes 1-2 hours to set, but I still recommend placing wax paper in between layers for stacking.
*The amount of cookies this recipe will make will depend on how thick it is rolled and how large the cutters are that you are using. Always watch for signs of doneness (color, texture) rather than going by the exact cook time.Notes:
Use the excess dough. After you do the first set of cut-outs, you can re-roll the excess dough to make more cookies. Repeat that process until you don't have any more dough left.
Check for doneness. I say 8-10 minutes as a guideline, but it's more important to keep an eye on the cookies to check when they're done (it will depend on the thickness). You want to take them out just before they are browning. If they are browned on the bottom, they will still be delicious but less soft.
Cool before frosting. Let the cookies cool completely before adding the frosting. If they're too warm it will just melt off.
If you're adding sprinkles, make sure you add them right away after you add the frosting so they stick. If the frosting sets, they will just slip off the top of the cookies.
Storage:Baked and frosted cookies will last in an airtight container at room temperature for up to a week or in the fridge for up to 2 weeks.You can also freeze them, but you will want to do so unfrosted. They will last in the freezer for up to 3 months.