Preheat oven to 180 degrees C. Grease and flour two 23cm round pans.
In a double boiler over lightly simmering water melt white chocolate, stirring occasionally until melted; set aside and cool to lukewarm. In a small bowl mix flour, sugar, baking powder and salt; set aside. In a large chilled bowl, whip cream until stiff peaks form; set aside.
In a large bowl, beat eggs for about 5 minutes, or until light and lemon coloured. Beat in 1 teaspoon almond essence and melted white chocolate. Fold in whipped cream. Fold in flour mixture, about 1/2 cup at a time. Pour batter between the two prepared pans.
Bake in the preheated oven for 35 to 40 minutes, or until a toothpick inserted into the centre of each cake comes out clean. Let cool in pan for 10 minutes, then turn out onto a wire rack and cool completely.
In a large bowl, melt white baking chocolate over low heat, stirring occasionally; cool to lukewarm. In a medium bowl on medium speed, combine melted white chocolate, icing sugar, butter, water and 1/2 teaspoon almond essence. Beat until smooth and of spreading consistency.