Place the all-purpose flour, baking powder, baking soda, ground ginger, allspice, nutmeg, and cinnamon in a small bowl. Stir thoroughly so the leavening agents and spices are evenly distributed throughout the flour, then set the mixture aside.
In a large mixing bowl, beat the softened butter together with the packed brown sugar using an electric mixer until the mixture becomes smooth and creamy.
Add the egg, molasses, and whole milk. Continue beating until all of the wet ingredients are completely incorporated.
Add the remaining flour mixture and continue mixing until the cupcake batter is smooth, evenly blended, and fluffy.
Line a muffin tin with cupcake liners. Spoon or pipe the gingerbread batter evenly among the prepared cups so the cupcakes bake as uniformly as possible.
Bake in an oven preheated to 350°F (175°C) for 20–25 minutes. The cupcakes are ready when a toothpick inserted into the center comes out clean.
Remove the baked cupcakes from the oven and allow them to cool completely before adding the frosting or decorative toppings.