Heat butter in a Dutch oven (or another large, heavy-bottomed pot with a lid) over medium heat. Add shallot, garlic, and pancetta and cook, stirring occasionally, until shallot is tender and pancetta has rendered, about 5 minutes.
Add pepper flakes, wine, and mussels; cover and bring to a boil, then reduce to a simmer and cook until the mussels have opened, 8 to 10 minutes (discard those that do not open). Serve with bread, if desired.
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.