The job that dropped the Sauce - even if it's your first time - all depended on your level, so saying, "It was Catching Horses" or "It was Burglary" is all depending on the level of the reader. I got it from Hunting Grizzly Bears - and yes, it was my first time doing it. My friend - also HIS first time doing it - got it from Catching Horses because he is of a different LEVEL to me.
If you go to TW-DB and look up the quest, you will see what jobs supply the Sauce. Now a quick point, as the level-requirements were CHANGED (confirmed by both Inno's staff and TW-DB's staff), don't go off the levels listed ON TW-DB to find out what jobs to do as - according to the site - I needed completely different ingredients and a different job to get the Sauce. (Bit annoying as I had stockpiled different ingredients to the ones I ACTUALLY needed.)
Going off the ingredients that I needed, I did the job associated WITH those ingredients (Hunting Grizzly Bears) and got the Sauce after just 1 x 15s job.
Yes you will have to wait a full YEAR now, but FOR next year, check out the site and the ingredients/job-needed and you can't go wrong.
It is a bit silly not giving even a HINT of what job to do in the quest-text though. I mean without looking at TW-DB, you would have to do every single job it is POSSIBLE for you to do, in the HOPE of getting the Sauce.