Preheat the oven to 350 deg F
Grease and line a cake pan.
Beat the butter and sugar until fluffy, beat in the egg yolks one by one. Add orange zest and juice.
Stir in the sifted flour and baking powder. Add the ground almonds, walnuts, spices and grated carrot. Mix together well.
In a separtae bowl whisk egg whites with a pinch of salt until stiff, then gently fold into the cake mix.
Cook for 50 mins.
Cool in the pan for 10 mins.
Turn out and leave for at least one hr.
Mix all of the icing ingredients together and spread generously over the cake, top with chopped walnuts.