Cake - Inexpensive Sponge: grease 2 9-inch layer pans or 13 x 9-inch oblong pan.
Beat with rotary beater until very light - 4 eggs. Beat in 2 cups sugar, 1/2 tsp salt, 2 tsp vanilla. Beat in 2 tbsp butter melted in 1 cup boiling hot milk. Sift together and beat in (very quickly) 2 cups sifted flour and 2 tsp baking powder.
Immediately pour into prepared pan. Bake at 350º F for 25 to 35 minutes.
Custard: whisk yolks in medium saucepan. Gradually add sugar, whisking until mixture is thick and lemon coloured, about 1-2 minutes. Blend in milk, whipping cream and cornstarch mixture. Place over medium low heat and cook, stirring constantly, until mixture thickens, about 3-5 minutes (do not boil, or mixture will separate).
Remove from heat and stir until slightly cooled. Blend in vanilla and nutmeg. Transfer to bowl.
Mom makes three batches of custard. Each batch should be done separately to avoid lumps.
To assemble: line bottom of glass bowl with layer of cake. With pastry brush soak with sherry. Spread thin layer of seedless raspberry jam or raspberry jelly. Top with well drained raspberries, then spoon 1 1/4 cup custard over berries.
Repeat layering twice more with cake brushed with sherry, jam or jelly, raspberries and custard. Place plastic wrap directly on surface of trifle. Refrigerate overnight.
Can be prepared up to two days ahead.
Before serving can be topped with whipping cream (2 cups with 2 tbsp sugar) and fresh raspberries.