Generally, the u003cstrongu003ecustard will thicken once the eggs are cooked enoughu003c/strongu003e. It continues to thicken as it cools down, so once the custard has had enough time to cool down completely it should thicken. u003cstrongu003eYou will know the custard is ready when you can draw a clean line through it on the back of a spoon.u003c/strongu003e