Charles Schiller

To ensure that your vegetables are cooked correctly, observe these rules:
When you’ve cooked vegetables that grow underground, such as potatoes, beets, and onions, they should feel soft when squeezed (carrots are the one exception). To avoid burning your hand, slide a fork or a knife into the root vegetable to determine doneness.
If it meets no resistance, the vegetable
is ready to eat.
Vegetables that grow aboveground, such as green beans, snow peas,
and asparagus, should have a crisp
yet tender texture when cooked.
(Exceptions: Eggplant, tomatoes, and winter squash, which grow on vines, should feel soft when ready to eat.)
They should resist being punctured when you poke them with a fork. Try breaking a green bean in half; if
you hear a quiet snap, it’s time to take them off the fire.
You can also gauge readiness by the color and taste: Well-cooked vegetables should retain a subtle variation of the original color and flavor. If they lose too much of either, you’ve gone too far.