Preheat the oven to 180°C and line a 12 hole cupcake tin with paper liners. Dissolve the instant coffee in 2 tbsp of warm water. In a mixer, beat the 120g of the butter and sugar until light and fluffy, gradually add the eggs, buttermilk, flour and half of the coffee. Beat until smooth. Divide the mixture between the cupcake liners and bake for 30 mins or until golden and cooked through. Allow to rest in the tin for 10 mins before removing. Leave to cool on a rack.
For the icing, sift the icing sugar into a bowl and add the remaining butter and coffee stir until smooth, top each of the cooled cupcakes with the icing and garnish with chocolate covered coffee bean.