Preheat the oven to 350 degrees F. Line a baking sheet with parchment paper.
Add the butter and granulated sugar to a large mixing bowl. Beat with a hand mixer on medium until creamed.
Beat in the sour cream until combined.
Add in the eggs and vanilla extract. Beat until combined.
Add in the flour, baking soda, baking powder, and salt. Beat just until the flour is incorporated. The dough will be sticky.
Divide the dough in half and place in plastic wrap to chill for 1 to 2 hours. This isn’t necessary but makes the dough more manageable. You can also sandwich the sugar cookie dough between two pieces of parchment paper and roll it out to ¼ inch thickness. Slide a baking sheet under the parchment paper and move it to the fridge.
Add the dough to a well-floured surface and dust the top of the dough with flour. Roll out to ¼ inch thickness. If you rolled your dough out between two pieces of parchment paper, skip the flour and cut them out while sitting on the piece of parchment paper.
Coat the cookie cutters in flour and cut out the cookies, making sure to dip the cutters back in flour after each use.
Place the cut-out sugar cookies on the prepared baking sheet about 2 inches apart.
Place in the preheated oven and bake for 10 to 12 minutes until puffy. It’s okay if the edges aren’t brown all. If the center looks raw or wet, bake longer until it’s puffy and the same pale white color as the edges.
Let cool for 5 to 10 minutes on the baking sheet before moving to a wire rack or paper towel to cool completely.
Store in an airtight container at room temperature for up to 3 days or in the fridge up to 7 days.
Beat the butter, 4 cups of powdered sugar, vanilla extract, and milk in a large mixing bowl.
Gradually beat in the 4 remaining cups of powdered sugar until the frosting is light and fluffy.
Add in 3 to 4 drops of gel food coloring.
Frost the cooled cookies and add sprinkles.
If you find the dough too sticky, you can add up to an additional ½ cup of flour into the recipe. Use simple shaped cookie cutters for this dough, because it will stick in crevices of more detailed cutters.