Grease the bottoms of 2 8-iiich layer-cake pans 1 1/2 inches deep, and line with greased waxed-paper circles.
Spread hazelnuts in a small shallow baking pan or pie plate, and toast in the oven at 300°F. 30 minutes.
Rub nuts together in a tea towel to remove as much crisp skin as you can.
Blend or grind nuts into fine bits.
Beat egg yolks on high speed in a small beater bowl until thick and lemon-colored.
Beat in icing sugar, cinnamon and rum flavoring.
Continue beating 5 minutes.
Fold in bread crumbs, 1 cup of the ground nuts and sifted baking powder.
Beat egg whites, salt and cream of tartar together in a large beater bowl until stiff dull peaks form.
With a whisk, fold in yolk mixture.
Divide batter between the 2 prepared pans, and bake at 350°F. 35 minutes.
Cool 10 minutes.
Cut around the cakes with a wet knife.
Leave until cold.
Invert, and shake out the cakes.
Peel off the papers.
Slice layers in half horizontally, using a serrated bread knife; then fill with cream filling.
Heat the apricot jam with rum, brandy or water.
When hot and bubbly, strain and spread over top and sides.
While jam is still warm, garnish with slivered hazelnuts.
Chill thoroughly before serving.