Butter and flour a 9″ by 2½” springform pan. Preheat the oven to 350°. Melt the chocolate in a double boiler and cool until lukewarm. Cream the butter with the salt, vanilla, and sugar. Add the egg yolks one by one to the butter-sugar mixture. Toss together the flour and walnuts in a separate bowl. Stir in the chocolate and nuts/flour. Beat the egg whites to soft peaks and stir ¼ of them into the chocolate mixture to lighten the batter. Fold in the remaining whites. Pour the batter into the prepared pan and bake 1 hour. Let cool in the pan for 20 minutes and push down the puffed-up sides so that they are flush with the middle. Remove the sides of the pan and invert the cake onto a cooling rack set over wax paper. (The bottom has now become the top of the cake.) Cool completely. Heat the Bonne Maman Apricot Preserves, push it through a sieve, and brush smooth preserves over the top and sides of the cooled cake. Let glaze set for about half an hour before icing the cake.
In a metal mixing bowl or sauce pan, scald the cream. Whisk in the coffee and add the chocolate. Stir 1 minute over the heat, then remove and continue to stir until the chocolate has completely melted. Cool from hot to warm and pour over the cake. Rotate the cake while spreading the icing evenly with a spatula. Chill the cake on its rack until the icing is completely set. Transfer (2 quiche bottoms are helpful) to a serving plate and refrigerate. Bring to room temperature before serving. Serve with whipped cream (a must!)
Note: The cake can be made in advance and freezes beautifully – even iced. (Freeze unwrapped first to set icing, then wrap well.)