Preheat oven to 250 degrees Have an ungreased 25 cm tube pan 4.5 in high. Beat egg yoks with half c sugar until very thick. Blend in chocolate, orange juice and rind. Mix 1c nuts with cake meal and potato starch. Fold into yolk mixture. With clean dry beaters, beat whites untill foamy. Gradually beat in remaining 1\2 c. sugar untill stiff peaks form. Gently fold yolk mixture into beaten whites. Turn into tube pan and bake 55 to 60 min., untill cake tests done. Invert pan on rack and let cake hang untill completely cool. Remove from pan and slice cake in half horizontally. Spread orange filling over top of bottom half. top with second layer. Coat cake with glaze. Garnish with remaining 1 c. nuts and the orange sections.
Orange filling melt preserves; stir in orange sections. cool 5 min.
Chocolate glaze heat orange juice. remove from heat, add chocolate, stiring until melted smooth. cool 5 min.