Preheat oven to 375 degrees F (190 degrees C). Spray a ceramic or glass baking dish with cooking spray.
Bring a pot of water to a boil. Add cauliflower florets and boil for one minute. Remove with a slotted spoon.
Cook pasta shells in the same water, following instructions on the Horizon package. To the drained pasta, add 1/2 cup milk (instead of 1/4 cup as shown on the package), 2 tablespoons butter, and packet of cheese powder.
Stir in cream cheese and Cheddar cheese; mix well until combined and cheese is melted. Add cauliflower and mix. Season with salt and pepper, if desired.
Spoon macaroni and cheese into prepared baking dish. Smooth out the top.
Melt 2 tablespoons butter. In a small bowl, mix together panko breadcrumbs, melted butter, salt and pepper. Sprinkle over the top of the macaroni and cheese.
Bake until the breadcrumbs are golden brown, 15 to 17 minutes.
