Spice it well; better, make thick the broth (Revised Version). The verb is used in Exodus 30:33, Exodus 30:35, of the concoction of the anointing oil, and the cognate adjective in Job 41:31 for the "boiling" of the water caused by the crocodile.
We are reminded of the "bubble, bubble" of the witches' cauldron in 'Macbeth.'