When the pressure-release valve starts to make a hissing noise, you’ve exceeded the pressure in your pressure cooker. Basically, the pressure cooker is telling you to lower the burner heat to maintain a high — but not too high — pressure.
If you cook on a gas stove, a simple turn of the burner knob causes the heat to drop almost instantaneously. If you have an electric range, turning the dial doesn’t elicit an instant response from the element. To overcome this problem, you can cook on two elements:
Set one stove element to high heat and one to a lower setting.
Set the lower-heat element to whatever setting keeps water boiling at a simmer.
Use the element set on high heat to bring the pressure cooker up to pressure.
You know its reached pressure when the release valve starts hissing.
After the pressure cooker reaches pressure, transfer it to the preheated element that’s set on the lower setting.
Don’t forget to turn off the high heat element after the transfer!