Can I use frozen blueberries?Yes—no need to thaw. Just increase chilling time to firm the filling.

How do I know the custard is done?It’ll coat the back of a spoon and hold a line when you drag your finger through it.

Can I use cornstarch for the sponge too?Yes—cornstarch makes the sponge light; just maintain the total flour weight.

How long does the cake keep?Store in the fridge (covered) for up to 4 days; best enjoyed within 2 days.

Can I freeze this cake?You can freeze individual squares. Thaw overnight in the fridge.

Can I reduce the sugar?Yes—ask for 10–20 % less sugar; berries and lemon juice provide natural sweetness.

Can I use low-fat milk?Yes, but custard may be less rich—adding a splash of cream helps.

What pan size should I use?Use a similar 28 × 18 cm pan. Larger pans yield thinner layers; smaller pans yield thicker.

Can I add citrus zest to the custard?Absolutely—add 1–2 tsp of lemon or orange zest for aromatic flavor depth.

My custard is too runny—what should I do?Return to gentle heat and stir until it thickens; cool slightly before pouring.