Beat the butter until softened and lightened in colour (3-4 minutes).
Add the icing sugar, a half cup at a time, beating well after each addition.
Add the vanilla, and beat well to combine.
Add the heavy cream, 1 tablespoon at a time, beating well after each addition, until your frosting reaches your desired consistency. You may need to add a little more cream if the frosting is too firm, or a little more icing sugar if it is too soft.
Divide the frosting into two bowls. Use the food colouring to tint one bowl of frosting light purple, and the other light blue.
Fit a piping bag with a star tip (Wilton #131), and use a spatula to fill half the bag with the blue frosting, and the other half with the purple frosting.
Pipe little flowers all over the top of each cupcake, starting at the centre and working your way out the edges.