Using a piping bag with medium-sized, star-shaped nozzle filled with the green frosting work from the centre of the cakes and pipe pointed branch shapes towards the edges of the cupcake. Keep doing this, turning the cupcake as you go, until you have created the bottom of a tree. Repeat with the next layer up, making the branches shorter. Do more layers, making the branches shorter as you get to the top. Decorate with the glitter, sugar balls and top with a sugar star.