Preheat oven to 350 degrees F. Butter and flour a 9 by 2-inch cake pan.
In a bowl, combine the chocolate and butter and melt over a double boiler. Set aside to cool. In a mixer, using a wire whisk, whip the egg yolks with 1 ounce sugar until light and ribbony. Beat in the chocolate mixture.
In another bowl, beat the egg whites and salt until soft peaks. Slowly add the remaining 3 ounces of sugar and continue to beat until stiff peaks. Fold in the flour and then fold in 1/3 of the egg whites into the chocolate mixture to lighten it. Fold in the remaining egg whites, gently but thoroughly. Pour into prepared cake pan.
Bake for 40 minutes or until done. To check for doneness, insert a paring knife in center of cake. It should come out dry. Remove from the oven and cool on a rack.
To make the apricot filling: puree the apricot preserves. Stir in brandy.
Slice the cake into 3 equal layers. Spread half of the apricot filling on the bottom layer. Top with a second layer of cake. Spread the remaining apricot filling and top with the last layer of cake. Chill for at least 30 minutes.
To make the glaze: in a bowl, combine the chocolate and butter. Melt over a double-boiler. Bring the cream to a boil. Stir into the melted chocolate. Cool until it reaches glazing consistency. Spread over and around the cake. Chill for another 30 minutes before serving. Serve a slice with Schlagobers or whipped cream.