This is one of my favorite ways to cook green beans — or a variety of other fresh vegetables — because they are tender, but still somewhat crisp (not mushy).
This same method can be used for zucchini & yellow squash with garlic & onion, because the vegetables get cooked through, but retain their shape and some texture. It is easy to over-cook squash and it gets mushy, but not using this method. Use this method for cauliflower also.
Begin with a pot which has a tight fitting lid. The pot should be just slightly larger than your quantity of vegetable, so that there is not too much room left over in the pot.
Add about an inch of cold, salted water (or chicken stock) to the bottom of the pot. Follow with prepared vegetables, sliced or chopped onion and garlic, and then drizzle some olive oil over the top. Finish with a little more seasoning on top of the vegetables.
Put the lid on the pot, and set it on a burner over HIGH heat. Allow it to come to a roaring boil, where steam is screaming out of the lid in the pot, but do not remove lid. After the steam is escaping rapidly FOR NOT MORE THAN 1 MINUTE then turn off the heat and leave the pot, tightly covered, right on the burner to cool down for 20 to 30 minutes.
If you prefer your vegetables even more crisp, then turn off the heat as soon as you see steam beginning to escape from the lid, and reduce the cool-down time to 10 minutes.
After the cool down, your vegetables are ready to serve — tender, but still retaining their original texture and not mushy.