1. Add 2 sticks (224g) unsalted butter and 1 ½ cup (300g) granulated sugar together in bowl and mix until light and fluffy (about 2 minutes).
2. Add 1 egg, 1 cup (240g) sour cream, 2 tsp (9.2g) baking soda, 1 tsp (2.2g) nutmeg, and 1 tsp (4.2g) vanilla extract and mix until well combined.
3. Gradually mix in 3 ¾ cup (450g) flour, cup by cup. The dough will become quite thick, this is normal. Once thoroughly mixed, cover and chill overnight.
4. Preheat oven to 375°F (190°C) and take dough out of refridgerator. Allow dough to come to room temperature for around 15 minutes.
5. Flour work surface and rolling pin. Roll batches of dough out to ⅛ inch (3 mm) thickness.
6. Cut dough into shapes with cookie cutters.
7. Place cookies onto cookie sheets and bake for 6-12 minutes. The time is dependent on your oven, size of cookie, etc. Be diligent with the first batch and how many minutes it takes for the cookies to puff up without significant browning around the edges. When the cookie browns around the edge, I find that it means the cookie is slightly overcooked. Experiment and do what works best for you and your tastebuds.
8. Place cookies on cooling rack, though a plate or wax paper on the counter are good options if you do not own cooling racks. They cool faster with more airflow, thus why racks are the better option if you have them. Let cookies cool completely before frosting them.
Instructions for Frosting
1. Mix 4 Tbsp (56g) unsalted butter and 6 ¾ cups (690g) powdered sugar together until combined and forming small clumps.
2. Add ¼ cup & 2 tsp (72.5g) whole milk and ½ tsp (2g) vanilla extract to the butter and powedered sugar mixture. Stir until frosting is smooth (around 2-3 minutes). Frosting will be thick, this is normal and correct!
3. Divide frosting into as many bowls as you want colors. Gradually mix in food coloring to reach your desired color saturation. If the frosting still remains too thick after adding the dye, feel free to add small amounts of milk (think drops not huge pours) until it is a spreadable consistency.
4. Spread frosting over cookies and immediately dust with sprinkles or sparkling sugar. Enjoy!
