Preheat oven to 350 degrees. Add liners to cupcake pan(s).
In a medium sized bowl or bowl of a standing mixer, cream together butter and sugar until light and fluffy (about 3 minutes).
Add in molasses, milk, and eggs and mix until incorporated.
In a separate bowl combine the flour, baking soda, baking powder, salt and spices (ginger, cinnamon, cloves and nutmeg). Mix until just combined.
Add the dry ingredients to the wet ingredients and beat just until mixed (do not overmix).
Scoop the batter into the cupcake liners filling each liner about 2/3s full.
Bake in over for 15-20 minutes or until a toothpick comes out clean. Cool completely on cooling rack before icing.
Eggnog Frosting (make while cupcakes are cooling)
Cream together butter and salt using a mixer.
Scrape down bowl with a spatula and mix in eggnog, vanilla and rum extract (if using).
Add in powdered sugar, slowly, 1 cup at a time, until desired consistency is achieved. NOTE: more eggnog may be added if the frosting is too stiff (dry).
Once desired consistency is reached, turn mixer on high and beat frosting for 3-5 minutes (this is easiest with a standing mixer using the paddle attachment). This will make your frosting really light and fluffy.
Spoon frosting into a piping bag equipped with a favorite piping tip (these cupcakes were frosted with a Wilton 1M tip).
Frost cooled cupcakes and sprinkle with ground nutmeg before the icing sets. Enjoy!