PreparationFor cream: Melt chocolate with 1/4 cup cream in heavy small saucepan over low heat, stirring until smooth. Cool to room temperature. In medium bowl, beat 3/4 cup cream to stiff peaks. Fold cream into chocolate mixture in 2 additions. Cover; chill until firm, about 1 hour. (Can be made 2 days ahead. Keep chilled.) For sauce: Scrape seeds from vanilla bean into heavy large deep saucepan. Add peach nectar and sugar and simmer until reduced to 1 1/2 cups, about 55 minutes. Whisk in butter. Cool. (Can be prepared 8 hours ahead. Cover; let stand at room temperature.) For shortcakes: Preheat oven to 325°F. Butter and flour 9-inch-diameter cake pan with 2-inch-high sides. Finely grind first 4 ingredients in processor. Using electric mixer, beat sugar and butter in large bowl to blend. Beat in eggs 1 at a time. Beat in extract. Stir in dry ingredients alternately with cream. Spoon batter into pan. Bake until tester inserted into center of cake comes out clean, about 45 minutes. Cool cake in pan on rack 10 minutes. Run small sharp knife around pan sides to loosen cake. Turn out onto rack; cool completely. Cut cake into 6 wedges. Cut each wedge horizontally in half. Place cake bottoms on plates. Top with some peaches, then sauce. Top with some cream. Cover with more peaches and sauce. Prop tops against side of shortcakes.
PreparationFor cream: Melt chocolate with 1/4 cup cream in heavy small saucepan over low heat, stirring until smooth. Cool to room temperature. In medium bowl, beat 3/4 cup cream to stiff peaks. Fold cream into chocolate mixture in 2 additions. Cover; chill until firm, about 1 hour. (Can be made 2 days ahead. Keep chilled.) For sauce: Scrape seeds from vanilla bean into heavy large deep saucepan. Add peach nectar and sugar and simmer until reduced to 1 1/2 cups, about 55 minutes. Whisk in butter. Cool. (Can be prepared 8 hours ahead. Cover; let stand at room temperature.) For shortcakes: Preheat oven to 325°F. Butter and flour 9-inch-diameter cake pan with 2-inch-high sides. Finely grind first 4 ingredients in processor. Using electric mixer, beat sugar and butter in large bowl to blend. Beat in eggs 1 at a time. Beat in extract. Stir in dry ingredients alternately with cream. Spoon batter into pan. Bake until tester inserted into center of cake comes out clean, about 45 minutes. Cool cake in pan on rack 10 minutes. Run small sharp knife around pan sides to loosen cake. Turn out onto rack; cool completely. Cut cake into 6 wedges. Cut each wedge horizontally in half. Place cake bottoms on plates. Top with some peaches, then sauce. Top with some cream. Cover with more peaches and sauce. Prop tops against side of shortcakes.