Combine passata, chicken broth and a sprig of oregano in a medium saucepan and bring to a simmer.
Meanwhile, heat oil in a separate saucepan over medium. Add couscous and garlic and cook, stirring, until beginning to toast, about 1 minute. Add remaining oregano and about a third of the broth. Simmer couscous in broth, stirring occasionally to prevent pasta from sticking, until liquid has almost fully evaporated. Repeat twice with more broth until couscous is tender, about 12 minutes total. Remove oregano sprigs.
Fold in mozzarella just before dividing among serving bowls. Drizzle with olive oil before serving.
Before her diagnosis, Caroline wrote a book on cakes called Cake Magic!. She started developing a birthday cake using her gluten-free mix found in that book. Check out other recipes she’s developing for her new life—and the stories behind them—on her blog, The Wright Recipes. Her next book, Soup Club, is a collection of recipes she made for her underground soup club of vegan and grain-free soups she delivers every week to friends throughout Seattle's rainy winter. (Available February 2021.)