Preheat oven to 350 degrees F. Line baking sheets with parchment paper or nonstick liner and set aside.
In a large bowl, whisk together the flour, baking powder, nutmeg, salt, cream of tartar, ground cinnamon, ground cloves and ground ginger. Set aside.
Using a stand mixer fitted with the paddle attachment, beat butter, sugars and cream cheese until light and fluffy, 2-3 minutes.
Beat in whole egg just until combined. Add egg yolks, vanilla extract and eggnog and beat just until combined.
With mixer on low, slowly add flour mixture and beat just until combined– don’t overmix!
Drop dough by the heaping tablespoon at least 3 inches apart on prepared baking sheets, about 6/sheet (you will need to use a cookie scoop as dough is very wet/sticky). Bake 12-15 minutes or until tops are set. Let cool for 3 minutes then transfer cookies to a wire rack to cool completely before frosting.
EGGNOG CREAM CHEESE FROSTING
Beat butter and 1 1/2 cups powdered sugar with handled mixer at medium-high speed until creamed together and light and fluffy, about 2-3 minutes. Add cream cheese, 1 piece at a time, beating thoroughly after each addition.
Add vanilla, ground nutmeg, ground cinnamon and eggnog and beat to combine. Beat in remaining powdered sugar. Add additional eggnog, if needed, a teaspoon at a time to reach desired consistency.
Evenly spread frosting on cooled cookies. Garnish cookies with crushed candy canes or ground nutmeg if desired.
*Do NOT microwave butter or cream cheese. Allow to soften at room temperature.