1. Preheat the oven to 350°F. Cook the pasta according to package directions until al dente. Drain the pasta and place back in pot. Meanwhile, bring a pot of salted water to a boil. Cut the cauliflower into small florets and boil for 2 minutes.
2. Dice the onion and the celery. Heat the oil in a skillet over medium heat and sauté the onion and celery until soft, 5 minutes.
3. Add the onion and celery to the cooked pasta. Fold in the Cheddar, cream cheese, mozzarella, milk and nutmeg. Mix over low heat until the cheese is melted, 2 minutes. Fold in the cauliflower and ham. Pour the pasta into a 13-inch x 9-inch baking dish and sprinkle the panko over the top. Bake until cauliflower is tender and the top is golden brown, 25 minutes.
Per serving: 537 calories, 26g fat, 13g saturated fat, 82mg cholesterol, 954mg sodium, 43g carbohydrate, 3g fiber, 5g sugar, 33g protein