We developed this recipe using an 8-quart pot with a stackable steamer insert. If you don't own one, a large pot and a folding steamer basket work well. Whisking the liquid from the stew into the steamed couscous is a key step, deeply flavoring it and helping it stay light and fluffy with distinct grains. Harissa can vary widely in heat level brand to brand. We liked Dea, which is sold in a tube. We use ¼ cup to flavor the stew, then mix another ¼ cup into the stew liquid just before whisking it with the steamed couscous. If your harissa is particularly spicy or you prefer less heat, reduce the second batch of harissa.