
Horseradish sauce is a prepared condiment of grated horseradish root in a creamy or vinegared base.
It brings pungency, salt and some body, and in Bloody Mary-style drinks it stirs in more easily than freshly grated root. Its heat is volatile: it builds for a couple of minutes after grating, then fades. The sauce in the jar is therefore past its peak, and freshly grated root is always sharper.
Prepared horseradish
The closest swap. Sharper and thinner than a creamy sauce, so start with half the measure and add more to taste.
Wasabi
Tube wasabi also starts at half the measure. It gets its bite from the same compound.
Freshly grated horseradish root
Far hotter, so begin with just a pinch.
English mustard
A small dab brings a similar nose-filling heat.
Keep it closed in the fridge. It does not spoil quickly, but it loses its heat quickly, so an old jar needs more per drink or replacing.