1. Add salt to boiling water to raise temperature above 100 C.(*)
2. Cook broccoli in boiling water for 2 to 3 mins. Sample to test if it is soft and crunchy.
3. Soak immediately broccoli in cold water.
Note (*) : This is the Principle of Physical Chemistry: water normal boiling point is 100 C, but with extra substance like salt added in it, more heat energy will be needed to reach the boiling point, so the temperature will raise above 100 C.