With broccoli the trick is to have the stems and the florets cook at the same rate. You can do this by removing the tough outer skin of the stalks. Simply peel the skin up from the base of the broccoli stalk.
Asparagus
The tender tips will cook more quickly than the stems. Avoid this by peeling the thickest part of the stems with a sharp knife.
Cauliflower
The stem and leaves of the cauliflower are edible but they are tougher and take longer to cook than the tender florets. After removing and discarding the outer leaves, rinse the cauliflower and remove the leaves and stem. Using a sharp knife carefully core the cauliflower. The leaves, stem and core can be reserved for use in soups, stock or stews if you wish.
Gently seperate the cauliflower crown into evenly sized florets - large or small depending on the recipe.
Leek
A relative of garlic, onion and shallot, the leek is a versatile and healthy vegetable which adds flavour without overpowering the other ingredients of a dish. Both the white root section and the green leaves of a leek are edible. The root tip should be trimmed , the top of the leaves cut off and discarded along with the toughest outer leaves.
You will be amazed at how much dirt and grit finds its way between the outer layers of a leek. And also how deeply within the layers you will still find traces of soil. If you are intending to use the green leaves then the easiest way to ensure that the leek is thouroghly clean is to run a slit up the length of the leek and open out the layers under running cold water.