Prepare Pie Base
Blend together flour, baking powder and salt and set aside. Line bottom of a 9 inch (23 cm) round cake pan with parchment or waxed paper. Do not grease.
Beat eggs at high speed in a medium mixer bowl for 5 minutes or until thick and light colored. Gradually add sugar and continue to beat until light and fluffy. Add lemon juice and stir in dry ingredients until well blended. Add hot milk all at once and mix quickly. Spread batter in prepared cake pan.
Bake in a preheated 375°F (190°C) oven for 25 minutes or until cake is firm to the touch. Cool in pan on a wire rack. Loosen sides with knife and remove from pan. Remove parchment paper.
Split cooled cake in half and spread Vanilla Cream Filling on bottom half. Place cake top on Vanilla Cream Filling. Spread Chocolate Glaze over top of cake. Refrigerate until serving time.
Prepare Vanilla Cream Filling
Mix together sugar and flour in a medium saucepan and stir in milk gradually until smooth. Cook over medium heat, stirring constantly until mixture thickens then remove from heat. Add a small amount of hot mixture to beaten egg and stir warmed egg into hot mixture. Cook one more minute while stirring constantly. Remove from heat and stir in vanilla. Cover the top of filling with waxed paper and let cool completely.
Prepare Chocolate Glaze
Melt butter and chocolate over low heat in a small saucepan until melted. Then remove from heat and add milk and vanilla. Stir in icing sugar and beat until smooth. If needed, add a few drops of warm water to obtain a thinner glaze.