For whatever reason this seems to be seldom discussed but the general idea is as follows in hand-wavey fashion:
Set up HSM with a non-exportable symmetric key, set key usages to "encrypt only" and as one step of the hashing scheme you use, encrypt your hash through the HSM. Protected HMAC key would work too.
The result is that an attacker who compromises your password db cannot perform offline attacks on your passwords anymore - they now need to do key extraction on your HSM or remain in your infrastructure and keep running guesses through the HSM where it is relatively easy to monitor what is going on and they can't do a bajillion operations per second anymore.
Wish everyone running large user dbs like yahoo or linkedin etc applied anchoring to their password hashing - it's a relatively simple measure for an org "at scale" to make hash dumps alone useless.
It did not win, and I believe it is only CPU hard and not also memory hard unlike argon2. Nevertheless techniques to do this have been explored academically and might make it into future designs.
In case it isn't obvious, please continue to use argon2 (I'm just mentioning this as a point of interest).