[Natalie's] Pistachio Cake

My good friend asked me for a pistachio cake, and while I'm not much of a fan of them myself, I said that I would bake one for her. Soon I got busy with work and study and my plan to surprise her with a delicious cake failed. However, yesterday that changed when I found I finally had some spare time on my hands. I made this delicious cake, and even I thought it was amazing! It's taken six month's...but here it is...Natalie's Pistachio Cake.
Note: For the icing I would recommend omitting the green colouring, unless you like the green colour, as pictured.

Ingredients for Cake
55g shelled pistachios
170g butter, at room temperature
170g caster sugar
3 eggs
110g self-raising flour
Ingredients for Icing
1 egg white
150g icing sugar, sifted
3/4 tsp lemon juice
green food colouring (optional)
extra ground pistachios (optional)

Method
Preheat the oven to 180 degrees (fan-forced) and grease and line one round cake tin. Finely grind the pistachio nuts in a food processor, then set aside. Beat together the butter and sugar until pale and fluffy. Beat in the eggs one at a time. Stir in the ground pistachios, then sift the flour on the top and fold in. Spoon the cake batter into the tin and bake for approximately 40 minutes. Test with a skewer to check. Turn the cakes out onto a wire rack and leave to cool completely. To make the icing, gradually wisk the icing sugar into the egg white until thick and glossy. Then beat in the lemon juice. Finally, you can add a few drops of green food colouring and pour the icing over the cake. Top with ground pistachios for decoration and taste, or silver dragées look effective. If you don't won't the food colouring (as pictured) leave it white and still top with pistachios. Enjoy!