If you decide to use Bird’s Custard powder, make two batches (2 pints) following the instructions on the back of the can.
If it doesn’t bubble long enough, the structure can break down and the custard will turn from thick to runny. The good thing is that if you’ve chilled the custard and it’s lost its thickness, you can put it back on the stove and reheat it to thicken it back up.
For the Custard
Heat the milk over low-medium heat, stirring frequently, until it just begins to simmer and steam rises from the surface.
Meanwhile, in a large mixing bowl, whisk the egg yolks, sugar, and cornstarch until light and smooth.
HINT: I use my KitchenAid for this, but only as a stand. I hand whisk but use the bowl of the mixer attached to the machine so that I don’t have to hold the bowl as well. This allows me to whisk and pour at the same time, which is needed in the next step.
Remove the hot milk from the stove. While whisking the egg yolk mixture constantly, dribble hot milk, a few drops at a time, into the yolks. Adding the hot liquid very, very slowly in the beginning will temper the eggs, allowing them to warm gradually so that they don’t curdle, or worse, scramble! Once you have dribbled in a good amount you can increase the amount of liquid you add at a time, whisking continuously until all the milk has been added.
Pour the contents of the mixer bowl into the saucepan and heat over medium, whisking constantly, until the mixture just comes to a boil. Once it reaches a boil, keep whisking, ensuring that the milk mixture does not stick to the bottom of the pan, until thickened, about 1-2 minutes.
Remove from heat and whisk in vanilla. Let sit for 5 minutes, then whisk in butter. Custard will be thick and smooth. Pour into a shallow bowl and cover the top with plastic wrap so that the plastic is touching the surface of the custard. This will prevent a skin from forming on top. Cool in the refrigerator until chilled.
For the Cake
Cut the full 13×9 cake in half horizontally (this is slightly different than the step photos in the post but achieves the same thing). Brush the cut sides of both cake halves with the cream sherry. Spread raspberry jam over the sherry. Cut the cake halves into small squares (about 1-2-inches).
For the Fruit
In a medium bowl, combine the strawberries, raspberries, sherry and sugar. Stir to coat and allow to macerate. Keep in the refrigerator until ready to assemble the trifle.
For the Whipped Cream
Combine the heavy whipping cream and the powdered sugar in a larger mixer bowl. Beat on high for 2 minutes, or until stiff peaks form. Keep chilled in the refrigerator until ready to assemble.
Assemble the Trifle
Place 1/3 of the cake cubes in the bottom of the trifle dish, jam side up. Top the cake cubes with 1/3 of the fruit, followed by 1/3 of the custard and finally with 1/3 of the whipped cream. Repeat layers two more times. Decorate the top with fresh fruit. Keep chilled until ready to serve.
