Beat egg yolks, thick and lemon colored. Beat in half (1/2 cup) sugar. Sift together and stir in flour, baking powder, and salt. Beat until stiff (holds a point), egg whites, cream of tartar. Beat in gradually the remaining sugar. Beat until very stiff and glossy. Gently fold in grated chocolate and vanilla. Pour into two (2) round layer pans lined with greased paper. Bake 25 to 30 minutes at 350 degrees. Put together with sweetened whipped cream. Garnish with flakes of chocolate.