Preheat the oven to 170C/325F. Line a 12 cup muffin pan with paper cases.
In a large bowl, beat the butter and sugar together with an electric mixer. Beat in the molasses, then beat in the eggs one at a time. Beat in the pumpkin puree and vanilla.
In a separate bowl, sift in the flour, baking powder, ginger and nutmeg and salt.
Alternating, add one-third of the flour to the egg mixture and stir to combine, then one-third of the milk. Repeat until all the ingredients are combined.
Spoon the batter into the muffin cases until nearly full. Bake for 15-20 minutes or until risen and firm to the touch. Leave to cool in the pan for 10 minutes, then place onto a wire rack to cool completely before adding the frosting.
For the frosting:
In a large bowl, beat the butter with an electric mixer until smooth, then beat in the vanilla. Sift in the icing sugar and add the milk, then beat until thick and smooth. If necessary, add a little milk or icing sugar to get the right consistency.
Spoon into a piping bag and swirl onto the completely cooled cupcakes. Add a mini gingerbread man to decorate.