Hello,
Don't use snail tea since it is end game, but recipes from Valdo's kitchen. You can also use scrolls from Horace's shop (village's place at night). You can easily get an Angel's set or a Hell's set of plug/ring at this point of the game.
Viewing post in Defeating the first Dark Knight?
Umm... No, you can't. This particular Dark Knight encounter happens IMMEDIATELY after repairing Hanth's Forge, before Horace's shop (and therefore vegetables for the higher-end recipes) is even unlocked. This also means any plug/ring sets above the Don't Touch My Set are also unobtainable at this point.
EDIT: I didn't mean to sound disrespectful or anything at all with my reply. I really love this game and thank you for all the hard work you put into it.