Blanching and shocking are exactly what they sound like! The technique is essential to properly cooking vegetables, ahead of serving, to a desired doneness, allowing you to reapply heat at the time you want to serve them. It is also a great way of keeping your vegetables longer so they don’t spoil or discolor. The technique works so well you can prepare tender vegetables several hours or even days ahead and then briefly sauté them, toss in a warm sauce or add to a roasted dish.
In the case of green vegetables the chlorophyll is released as a gas in the cells of the vegetable during the blanching process. In the shocking process the gas is trapped in those cells and stays there giving the vegetable its bright color. If you do not shock the vegetable the cooking process will continue even after you remove it from heat and will turn it an unappealing khaki grayish color.
To properly blanch and shock vegetables, prepare a large pot of boiling salted water.
Also prepare a large bowl of ice water with a large strainer that fits into the bowl.
Clean your vegetables and trim to the desired shape and size and place in the pot of boiling water. For the average sugar snap pea or haricot vert the amount of time blanching may be as little as 1 minute. Remove the vegetables from the boiling water and place in a strainer in ice water and allow to thoroughly chill without soaking. Remove the strainer and place the vegetables on a separate plate or bowl to dry.
By using the strainer you can blanch and shock the vegetables in batches without having to change and re-heat the water each time. This is a great process to use for a variety of vegetables that require different amounts of time to cook. Start with the lightest color vegetable first and then proceed to the darker vegetables.