In a saucepan, whisk together milk, sugar, cornstarch, vanilla extract, and salt. Cook over medium heat until thickened, stirring constantly.

Remove from heat and let cool completely.

In a mixing bowl, beat the chilled heavy cream, powdered sugar, and vanilla extract until soft peaks form.

In a trifle dish, layer half of the sponge cake cubes, followed by half of the custard, half of the berries, and half of the whipped cream.

Repeat the layers with the remaining ingredients.

Chill in the refrigerator for at least 2 hours before serving.