Preheat oven to 350°F and prepare 2 cupcake pans with liners. In a large mixing bowl, add the eggnog, melted butter, oil, eggs and vanilla, then beat together with a whisk until the mixture is smooth and well-combined. Set aside.

In a separate medium mixing bowl, add the flour, white sugar, brown sugar, baking powder, salt, cinnamon, allspice and nutmeg. Whisk until well combined, then pour the dry mixture into the wet mixture and whisk together until smooth. Finally, add the raisins and fold them into the batter.

Pour the cupcake batter into a prepared cupcake pans, then place into the oven to bake for 18-20 minutes, or until an inserted toothpick comes out clean. Allow to cool completely before frosting.

Add butter to a stand mixer fitted with the whisk attachment. Beat on high until butter is doubled in volume, and looks light and fluffy.

Turn the stand mixer to low and slowly add the confectioners sugar. Beat until completely incorporated, then add in the eggnog and vanilla. Beat until well-combined and fully incorporated. Transfer to a piping bag with star tip.

Pipe onto cupcakes, then sprinkle lightly with nutmeg.