Bake at 385° Covered for 30 Minutes then Uncover it and Back in the over for another 30 Minutes.
For Best Results Let it Sit, for at least 20 to 30 minutes, it will still be Hot but it will Set very Nicely. Trust me, it's worth the Wait
I Would Also recommend using Boxed Soy Milk, or Just Boxed plant milk of your choice because it's thicker in consistency Perfect for this Dish. No need to worry about Evaporated milks or heavy cream. Boxed plant milk will do the trick.
Also, as we are layering our mac, on the first layer, it may be helpful to pour half of the custard in, then after, the final layer, pour the remaining custard liquid, just so it goes down into every macaroni Perfectly