If you own a thermometer, use it. Stick it in the very center of the flan.
You want 175°F to 180°F (80°C to 82°C). Any lower, and it’s raw. Any higher, and you’ve made an omelet.
Remember: flan keeps cooking after you pull it out. That’s called “carryover cooking.” Remove it at 175°F; the residual heat will finish the job.
Why You Shouldn’t Trust Your Oven
Ovens are liars. They run hot or cold. And a water bath (bain-marie) makes everything goofy.
The water bath is supposed to keep things gentle. But it also creates steam, which confuses your bake time.
Flan Recipe - Craving Home Cooked
So your recipe says “50 minutes.” My oven says “who knows?” That’s why you jiggle and measure.