Step 1

Preheat oven to 350°F. Line two cookie sheets with parchment paper or silpat baking mats.

Step 2

Cream butter and 1 cup granulated sugar using a stand or a hand mixer until fluffy. Mix in egg and vanilla, then mix in baking soda, cream of tartar, 1/2 teaspoon cinnamon, nutmeg and salt. Slowly mix in flour until dough is combined.

Step 3

Place remaining 1/4 cup granulated sugar and 2 teaspoons cinnamon in a small bowl. Scoop 2 tablespoon sized cookie balls and roll them in the cinnamon sugar mixture and place on cookie sheet.

Step 4

Bake 2 tablespoon sized balls of cookie dough for 10-13 minutes or until they are cracked on the tops and just lose their glossy sheen. Err on the side of under baked for best results. Let cookies cool completely before frosting.

Step 5

To make frosting: beat butter until smooth with a hand mixer in a large bowl. Slowly beat in powdered sugar until mixture is crumbly. Add salt and 1 tablespoon eggnog. Mix, adding more eggnog as desired for spreading consistency (up to 1 additional tablespoon). Frost cookies, sprinkle with cinnamon.

Step 6

Store loosely covered in an airtight container for up to 3 days or freeze for up to one month.