boiling down, reduction, boil-off
Мы сняли с огня закипевший суп.
We took the soup, which had come to a boil, off the heat.
Она услышала звук закипающего супа и выключила газ.
She heard the sound of the soup coming to a boil and turned off the gas.
Она сняла с огня закипавший чайник.
She took the kettle that was coming to a boil off the heat.