Could I just use regular couscous, rather than Ptitim, or Israeli couscous?
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Sure, even the correct ratio of water to couscous is there. You will just have a different texture. Sounds very nutritious and toothsome.
I personally like Israeli couscous a lot more than standard couscous, and think it has a very different affect. But as nutcakes notes, you can probably substitute a couscous or, for that matter, a multi-grain or brown rice with successful results.