Green Chile–Harissa Potato Gratin

There was a point in my career when I became obsessed with North African flavors. It began while I was living in France when I made an Algerian friend who made couscous from scratch. Later I discovered Paula Wolfert’s wonderful book Couscous and Other Good Food from Morocco. And then I went to work at a restaurant where ras el hanout and harissa were incorporated into French bistro-style dishes. Traditionally, harissa—an aromatic spice paste—is made with a red piri piri