Preheat oven to 350°F (177°C). Line 12-count muffin pan with cupcake liners.
In large bowl, beat the butter and brown sugar together on medium speed until creamy. Beat in the egg until combined, scraping down the sides as needed. Beat in the milk, molasses, and vanilla on medium speed.
In a separate bowl, whisk the flour, baking powder, baking soda, salt, cinnamon, ginger, nutmeg, and allspice together until combined.
Add the dry ingredients into the wet ingredients. Mix until just combined.
Fill cupcake liners 2/3 of the way full.
Bake for 18-22 minutes or until a toothpick inserted in the center comes out mostly clean.
Allow to cool completely before frosting.
Beat the cream cheese and butter together on medium speed until smooth, about 2 minutes. Add icing sugar and 1 Tbsp milk. Beat for 2 minutes. Add the vanilla and 1 more Tbsp milk if needed to thin out. Beat for 1 minute.
Swirl on the frosting using an icing bag fitted with your desired tip. Sprinkle gingerbread man sprinkles or a pinch of cinnamon to garnish.