Haselns Kuchen (hazelnut Cake)

Mix the sugar and egg yolks with a mixer until creamy (this takes longer than you'd suspect - mix for a longer rather than shorter amount of time if in doubt). Mix the flour and nuts together, then add them to the egg mixture and mix well. Whip the egg whites until stiff and then fold them into the nuts/egg yolk mixture. Put batter in a well buttered and floured 10" spring-form pan. Bake at 320 F for 60 minutes. Glazing: Mix powdered sugar and liquid; add a little water if necessary. Blend. Spread over thoroughly cooled cake and let sit for awhile to settle before cutting the cake.