In this recipe, the Instant Pot is being used as a self-contained steamer—not as a pressure cooker. So you need to leave the pressure valve set to Venting when cooking the custard. Do not seal it. I grew up watching my mother make this recipe in a stovetop pressure cooker. It was one of the first things I learned to make, when I was fourteen years old. It’s a lot lighter than a flan, which is how I justify eating a lot of it in one sitting!