Prepare the Dough: Combine the flour, baking soda, cream of tartar, and salt in a bowl. In another bowl, cream the butter and sugar until light and fluffy. Add the egg and vanilla extract, mixing well. Gradually add the dry ingredients to the wet ingredients, stirring until a soft dough forms. Chill the dough for at least 30 minutes to make it easier to handle.

Shape and Roll: Preheat your oven to 350°F (175°C). Roll the chilled dough into 1-inch balls, then coat each ball in the cinnamon-sugar mixture. Place the balls on a parchment-lined baking sheet, spacing them about 2 inches apart.

Bake: Bake the cookies for 8-10 minutes. Remove from the oven and use the back of a spoon to press a small indent in the center of each cookie while they’re still warm. Let the cookies cool completely on a wire rack.

Prepare the Filling: In a mixing bowl, beat the cream cheese, powdered sugar, eggnog, and nutmeg until smooth and creamy. Transfer the mixture to a piping bag or use a spoon to fill the indents in the cooled cookies.

Assemble: Pipe or spoon the filling into the indentations of each cookie. For a festive touch, sprinkle the tops with a pinch of nutmeg. Allow the filling to set for about 10 minutes before serving.

Serving Suggestions

Serve these cookies alongside a warm drink like hot cocoa, spiced cider, or eggnog. They’re also perfect for a holiday dessert platter or as a sweet treat in gift boxes.