Preheat oven to 350F. Coat a 9-inch layer cake pan with cooking spray; line bottom with wax paper and coat paper with spray.
To prepare cake, sift together flour, baking powder and salt. In a mixing bowl beat butter, 1/2 cup sugar, egg yolks and vanilla until well blended. Gradually add flour mixture alternately with milk, blending well after each addition.
In another bowl beat egg whites until foamy. Gradually add remaining 1/4 cup sugar and beat until stiff peaks form. Stir one-third of whites into flour mixture; fold in remaining whites. Pour into prepared pan. Bake 30 minutes or until a tester inserted in center comes out clean. Cool in pan on wire rack for 10 minutes. Remove from pan, peel off wax paper and cool completely, right side up, on rack.
To prepare pastry cream, in a medium bowl whisk egg yolk, sugar, cornstarch and 1/2 cup milk until well blended. In a small saucepan, heat remaining milk until hot. Gradually whisk hot milk into yolk mixture. Return all of mixture to pan; cook, stirring with a wooden spoon until thick and bubbly; turn to low heat, cook and stir 1 minute. Remove from heat and stir in butter and vanilla. Pour into a bowl; press plastic wrap directly onto surface and cool to room temperature.
With a serrated knife, cut cake horizontally in half to make 2 layers. Place bottom layer, cut side up, on plate. Whisk pastry cream and spread on top. Cover with top layer, cut side down.
To prepare chocolate glaze, in a small saucepan heat cream over medium-low heat until bubbles form at edge. Add chocolate and whisk until smooth. Remove from heat and cool about 7 minutes or until thick enough to spread. Spread on cake.