PREPARE CAKE LAYERS: Heat oven to 350 degrees.Grease and flour two 23 cm round cake pans.In large bowl with electric mixer at medium speed, beat quarter cup butter,1 cup sugar,eggs, two third cup milk,1 tsp. vanilla and baking powder about 4 minutes until thoroughly blended and smooth. Spoon batter into prepared pans;bake 30 minutes until wooden pick inserted in center of each layer comes out clean.Remove layers to wire racks to cool completely. PREPARE EGG CUSTARD: In 2 litre saucepan,stir two third cup sugar,cornstarch and salt until thoroughly mixed;slowly stir in 2.5 cups milk until smooth.Bring to boil over medium heat,stirring constantly;cook 1 minute until mixture boils rapidly and thickens.Remove from heat; very slowly pour lightly beaten egg yolks into hot mix ture,stirring rapidly and constantly to blend and keep smooth.Return mixture to low heat;cook 1 minute longer.Do not allow to boil.Remove from heat;stir in 1 tablespoon. vanilla.Cool completely,stirring frequently. PREPARE CHOCOLATE G! LAZE: In small heavy saucepan over very low heat, melt chocolate and 1 tablespoon. butter,stirring frequently until blended and smooth.Remove from heat;stir in confectioners sugar and quarter cup milk until blended and smooth.Keep warm,covered. To assemble: Using sharp serrated knife,carefully cut cooled layers in half horizontally.Place one layer,cut side up,on serving platter; spread with one third cooled custard.Repeat with remaining cake layers and custard,ending with cake layer,cut side down.Spoon warm glaze over top of cake,letting mixture drip down sides.Makes dozen to 16 servings.