Some say the best sweet potato casserole is covered in marshmallows; others swear by a buttery streusel or toasty maple-slicked pecans. While I firmly believe crunchy contrast is essential to this classic Thanksgiving side dish, there’s one small problem: I’m allergic to nuts. My sweet potato casserole recipe swaps the nuts for crispy, sweet-and-salty cornflakes—the marshmallows can stay.