First, you'll need to trim the asparagus. Cut off about an inch from the bottom of the stalk. You can save the trimmings for vegetable stock.: The smell of fresh asparagus is green and slightly grassy as you slice the ends. When you bend a stalk near the bottom it should snap cleanly where the tender part begins, a visual cue that the woody portion is gone. Trimming saves unpleasant chewiness in the finished dish and removes fibrous texture that can mask sweetness. A common mistake is cutting too little, leaving a tough bite, so taste one trimmed stalk raw to check tenderness.
In a saucepan or a large pot, bring water to a boil and salt it.: Listen for a rolling boil before you add the asparagus , the water should sound lively and produce steady steam. The salted water seasons the vegetable and raises the boiling point slightly, which promotes even cooking. If you under-salt, the spears may taste flat after blanching. Avoid adding the asparagus to water that is only gently simmering, because it will make timing unpredictable.
Fill a large bowl with cold water, add ice cubes to it, and set aside.: The ice bath should be noticeably cold to the touch, with clinking cubes and a crisp chill that contrasts the hot pot. This immediate temperature reversal locks in color and texture. If the ice bath is too small or warms quickly, the cooling effect is lost and the asparagus will continue to cook. Keep extra ice nearby if you are blanching multiple batches.
Add the prepped asparagus to the boiling water, and set your timer to 2-3 minutes. The broccoli should be bright in color, crisp and tender at the same time.: When the spears hit the boiling water you may hear a brief hiss, and the stems will deepen to a vivid green within a minute. The ideal feel is a crisp tender bite that still offers resistance, not limp. The statement about broccoli in the original text appears to be an oversight, but use the same visual cues for asparagus . Overcooking is common, which turns spears soggy and dull in color, so set a timer and sample one spear at the earlier end of the time window.
Remove from the saucepan with a spider strainer, and plunge into the ice bath to stop the cooking process. Leave for 1 minute, then drain and use as desired.: You'll hear a soft splash as spears hit the ice water and see steam collapse into cold. Leaving them in the bath for about a minute chills them through and seals that bright green. Drain on paper towels or in a colander, then use as desired. A frequent error is skipping the ice bath or leaving spears in hot water; both cause continued cooking that ruins texture and color.