In a medium bowl, sift together all dry ingredients (flour, baking soda, baking powder, salt and nutmeg). Set aside.
In a separate large bowl, with an electric blender, beat together the butter, sugar, and vanilla extract until fluffy. Add eggs one at a time until creamy. Interchangeably, add the dry ingredients and the sour cream into the butter mixture, adding a little of each at a time. When it’s ready the cookie dough will form into one big ball of cookie dough. Place the bowl of dough in the refrigerator for about an hour or longer so the dough will be easy to roll out.
Turn the dough onto a lightly floured surface and roll out to about 1/2 inch thick. Use the desired cookie cutters to make shapes or you can roll into balls. Place the cut out cookies onto a baking sheet lined with parchment paper. Place in the oven for exactly 10 minutes. Remove pan from the oven. Remove cookies from the cookie sheet and place on a cooling rack to cool before decorating.
To make buttercream: In a medium bowl, beat the butter until creamy. Interchangeably add the powdered sugar and milk until creamy. Add the vanilla extract, salt and food coloring until the desired color is reached. Pipe as desired on cooled cookies. Place frosted cookies in the refrigerator for 20 minutes to allow the frosting to set and then enjoy.