Carrot Cake with Butter Cream

Cake: Sieve together the flour, baking powder and soda, cinnamon and salt. Mix in the walnuts. Blend together the oil and sugar. Add the eggs, one by one, then the carrots and blend until smooth. Pour over the flour mixture and mix until smooth. Butter and flour a ring cake mould. Fill with the batter and bake in pre-heated oven at 200C for 45 min. until a toothpick comes out clean when inserted in cake centre.;Butter Cream: Beat butter until light and fluffy. Add egg yolks and beat again. When it starts getting foamy, add the vanilla, salt and then sugar, slowly. Beat until the sugar dissolves in the cream.