I'm posting this because I realize that one day I'll want to post my dynasty, where my founder supermaxed cooking, and someone's going to ask "hold up, how did you complete all of those foreign recipe ops?"
Simple, really. Buy all the recipes from the bookstore that you can. Every time your sim levels up in cooking, take some time out of your sim's day to read recipe books up to that level. Once they know all the regular recipes that they possibly can, make sure they talk to every natural cook in the culinary career and trade kitchen secrets. You can do it once a day per person, which can mean up to three or maybe even more recipes depending on what town you're in (My experience with this lies solely in Twinbrook, where you have three potential recipe givers, two of whom live right near the dynasty lot). If they know every regular recipe for their level, the only thing left to learn from others are foreign recipes. And bam! Nigh-guaranteed falafel, crepes, and whatnot when you need it.
I'm probably not the first person to think of this.
And its usefulness is pretty much limited to founders. When I had a cook for the second generation in a dynasty, he bought foreign recipes the old-fashioned way.