Cream together butter, sugar, and salt in a stand mixer with paddle attachment.
Mix in the eggs and vanilla extract.
Add flour, cornstarch, and nutmeg. Mix on low until fully incorporated.
Stir in the sour cream.
Use a rolling pin to roll all of the cookie dough out to a thickness of ¼ inch. You may also work with half of the dough at a time if needed. If your cookie dough is sticky you may lightly flour your surface. Cut cookie dough into desired shapes using your favorite cookie cutters.
Bake at 375 degrees for 10 minutes or until edges are lightly browned. Do not overbake. Remove from oven. If decorating right away, allow cookies to cool completely before icing. If storing, place them in an airtight container for up to 2 weeks or in the freezer for a few months.