Custards, especially “still” or baked custards, have a reputation for being tricky things to make. I suppose that’s somewhat true. We’ve all had our share of soupy, over-cooked quiches, after all. But it doesn’t have to be this way assuming you a) follow your recipe and b) know your oven.
For custard baking is a sort of gambit. You’re shooting for a very narrow temperature range, the point at which your egg proteins coagulate and the custard sets. In the case of some very delicate custards a mere five degrees can mean the difference between velvet goodness and disaster. Which is why custards are generally baked at low temperatures.
Oh sure, there are some daredevils out there who bake their custards (especially their pumpkin pies) at high heat, but you really have to know what you’re doing to pull a stunt like that. For baking custard at high heat is like driving on ice: everything is peachy until it comes time to stop, at which point you end up in someone’s front yard. Probably an off-duty cop, whose wife had just left him, but who spent the afternoon laying out all his expensive outdoor Christmas decorations anyway. Oof.
Which is why responsible bakers drive slowly and deliberately down the slippery custard street, blinkers on, hands at the 10 and 2 positions, gently applying the brake as they approach their stopping point. Nice to see you again officer Petry, very sorry to hear about your domestic difficulties.
Much of the time this slow creep is accomplished in a 325 oven, usually in a water bath You can tell a nearly finished custard because it only just jiggles and doesn’t slosh when you tap it. Also there is frequently a subtle color difference in the very center. This is the point to take it out of the oven, the point just before its is completely cooked, as residual heat will finish the job as it sits.