
Wasabi paste is the pungent green condiment sold in tubes, usually more horseradish than real wasabi rhizome.
A dab is enough. Dissolve it in a little of the liquid first: a lump of paste does not disperse when shaken and lands whole in one mouthful. The heat is nasal, not on the tongue: it clears the sinuses and fades, so a savory drink can carry it without tasting hot. Vodka, cucumber, citrus and soy are its usual company.
Prepared horseradish
The closest swap in the same amount. It shares a similar heat but tastes much coarser. The added vinegar and salt make things sharper, so be sure to fine-strain.
Fresh wasabi root
Grate it right before mixing and use the exact same measure. The heat fades fast, leaving a mild green flavor behind.
Hot mustard powder
A small pinch brings plenty of heat, but shifts the taste toward mustard.
Keep an opened tube tightly closed in the fridge and use it quickly. The pungent compound is volatile and starts escaping as soon as the tube is opened.