Make the Cookies:

1. Preheat oven to 350°F (175°C) and line two baking sheets with parchment paper.
2. In a large bowl, cream the butter and brown sugar together until light and fluffy. Add the egg and molasses, mixing until combined.
3. In a separate bowl, whisk together the flour, baking soda, ginger, cinnamon, cloves, and salt. Gradually add the dry ingredients to the wet ingredients, mixing until a dough forms.
4. Scoop out 1-tablespoon portions of dough, roll into balls, and coat in granulated sugar. Place the balls 2 inches apart on the prepared baking sheets.
5. Bake for 8–10 minutes or until the edges are set but the centers are soft. Allow cookies to cool on the baking sheets for 5 minutes before transferring to a wire rack to cool completely.

Make the Eggnog Frosting:

1. In a medium bowl, beat the butter until creamy. Gradually add the powdered sugar, eggnog, nutmeg, and vanilla extract, beating until smooth and fluffy.

Assemble the Sandwich Cookies:

1. Spread or pipe a generous layer of eggnog frosting onto the flat side of one cookie. Top with another cookie to create a sandwich. Repeat with remaining cookies.