Line a large glass bowl with 1-inch cubes of sponge cake or 1/2 small (purchased) pound bake. "Butter the layer with strawberry or raspberry preserves. Douse the cake with 3 to 4 tablespoons of rum or sherry. Add a layer of pineapple, fresh strawberries (sliced) or very well-drained frozen strawberries or raspberries. Cover with 1/2 of the custard sauce. Repeat the layer. Add the custard sauce; frost with whipping cream and garnish with pineapple and strawberries. Custard Sauce: Beat slightly: 3 or 4 egg yolks. Add 1/4 cup milk, 1/8 teaspoon salt. Scald and stir in slowly 2 cups milk. Place the custard in a double boiler and cook over very hot, not boiling, water, until it begins to thicken. Strain and cool the custard. Add 1 teaspoon vanilla, rum or sherry and a little grated lemon rind. Trifle is best when made just before serving. Refrigerate bowl; line with cake, etc. but put together about an hour before serving dinner.