Dissolve 1 tablespoon instant coffee in 2 tablespoons of boiling hot water. Mix until combined, then set aside.
In a large bowl, beat room temperature butter until fluffy - about 5-7 minutes.
Add in 1/3 cup icing sugar and mix until incorporated, then add 1/2 tablespoon of hot coffee mixture, and 1/2 tbsp of cream. Mix in completely.
Repeat process, until all the ingredients have been used up.
Beat until incorporated and frosting is light and fluffy.
If frosting is too soft, add in more icing sugar (2 tbsp at a time), if too frosting is too stiff, add a little cream (1 teaspoon at a time)
Transfer frosting to a piping bag, fitted with a Wilton 2D tip.