Prepare the vanilla custard according to package instructions.
Slice the fresh strawberries and set aside.
Cube the sponge cake into bite-sized pieces.
In a glass bowl, layer a third of the sponge cake at the bottom.
Add a layer of vanilla custard over the cake.
Top with a layer of sliced strawberries.
Add another layer of sponge cake on top of the strawberries.
Repeat the layers until all ingredients are used, finishing with custard.
Spread whipped cream on top and garnish with remaining strawberries.
Chill in the refrigerator for at least 1 hour before serving.