To make the cupcakes, preheat the oven to 350F (175C) whip the butter and sugar together.
Add the eggs and vanilla and whip until the mixture is light.
Add the instant coffee and mix. (You can use a lesser amount of coffee, but a stronger coffee flavor complements the frosting very well).
Mix the flour and baking powder (dry ingredients) in a bowl.
Now, slowly incorporate the dry ingredients and the rum alternately (in a dry-wet-dry sequence) with the butter mixture.
Divide the mixture into 12 greased cupcake moulds and bake at 350F until a skewer comes out clean (about 15-20 minutes).
For the frosting, whip the cream cheese and vanilla until soft.
Slowly add cream and icing sugar, while whipping, until stiff peaks are formed.
Pipe the frosting on cooled cupcakes. Dust cocoa powder on top.