Preheat oven to 350°F, line a 12-count cupcake tin with liners; set aside.
In a medium size bowl, whisk all of the dry ingredients and spices together: flour, baking powder, baking soda, salt, cinnamon, ginger, nutmeg, and allspice; set aside.
In a large bowl with a hand mixer or in a stand mixer with a paddle attachment, beat butter and brown sugar together until creamy. Then, beat in the egg, and then beat in the milk, molasses, and vanilla.
Gradually add in dry ingredients and mix just until all the flour is combined into the wet mixture.
Divide batter evenly among the 12 cupcake liners and bake for about 20 minutes or until a toothpick comes out clean with a few crumbs. Set on a cooling rack to cool.