In a blender, combine egg yolks, harissa, lemon juice and 1 tablespoon water. Blend until well-combined. With motor running, pour unsalted butter into blender jar in a thin stream until a thick sauce forms. Season with salt and pepper and set hollandaise aside.
Heat 2 tablespoons oil in a large, heavy skillet over medium-high until hot. Add sweet potato and cook, stirring occasionally, until sweet potato is crispy and charred in places, about 8 minutes. Stir in tomatoes and radicchio and cook until they are wilted and charred, 3 minutes. Season with salt and pepper.
Fry 4 eggs in remaining 1 tablespoon oil in a large skillet over medium heat. Serve hash topped with an egg and hollandaise.
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.