From player sources there is conflicting information about this recipe's drop but in all cases I was unable to find definite or official sources. So just trying to confirm which one of these statements is true:
1) Arenanet closed Tazza's loot table some years ago and haven't reinstated it, so she drops nothing and therefore does not drop this recipe.
2) Tazza drops the recipe but you have to engage her with Kaeyi and not pull her away separately.
3) Kaeyi drops the recipe so you have to defeat him before defeating Tazza.