Preparation

• In a large bowl, whisk together the flour, ginger, cinnamon, nutmeg, cloves, baking soda, and salt. Set aside.
• In a separate large bowl, using an electric mixer on medium speed, beat together the butter and brown sugar until no lumps remain. Add the egg, egg yolk, vanilla, and molasses, and continue beating until well combined.
• Turn the mixer down to low and slowly beat in the flour mixture until everything is combined. Turn off the mixer and scrape down the sides of the bowl as necessary. Cover the bowl with cling wrap and refrigerate for 30 minutes or up to 24 hours.
• Preheat the oven to 350F and line two cookie sheets with parchment paper or silicone baking mats. If the dough has been chilling for over 2 hours, allow it to sit at room temperature for about 20 minutes.
• Form the dough into cookie balls about 1.5 tablespoons in size, rolling them in granulated/turbinado sugar, and place them 2 inches apart on the lined cookie sheets. Bake for 8-10 minutes until the tops are just set. Allow to cool for 5-10 minutes before transferring to a wire rack.
• While the cookies are cooling, make the eggnog frosting. Beat the butter on medium speed until well softened. Beat in the icing sugar about ½ cup at a time until 2 cups have been beaten in. Add the eggnog a tablespoon at a time and optional rum extract, adjusting the sweetness with extra powdered sugar or eggnog as necessary.
• Frost the bottom of one cookie with about 1 tablespoon of frosting, then place a second cookie on top to create a sandwich. You'll end up with about 16-18 sandwiches total.