Combine vegetables, chicken broth, bay leaf, and nutmeg in a medium saucepan and season with salt and pepper. Bring to a boil and reduce heat to medium to simmer until vegetables are tender, 15 minutes. Remove bay leaf.
Using an immersion blender (or standard blender, working in batches), puree soup until smooth. Stir in sour cream and lemon juice. Serve soup topped with trout pieces alongside crusty bread.
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, Catalan Food, written with chef Daniel Olivella, comes out in early September from Clarkson Potter.