Preheat the oven: Preheat oven to 400°F with a rack in top third of oven.
Melt butter and cook aromatics in a skillet: Melt butter in a large (oven-safe and table-worthy, if you have it) skillet over medium. Add onion and garlic; cook, stirring often, until softened, about 6 minutes.
Reduce heat, add seasonings and soft cheese: Reduce heat to medium-low. Add soft cheese, salt, pepper, and nutmeg; cook, stirring, until cheese is melted, 1 to 2 minutes.
Add spinach, parmesan, and cream: Stir in spinach and ¼ cup Parmesan. Stir in cream. If your skillet is not oven-safe, transfer the mixture to a 13-by-9-inch baking dish.
Top with crumbs, more cheese and bake: Sprinkle with cracker crumbs and remaining ¼ cup Parmesan. Bake until golden, 10 to 15 minutes.
