Instructions

1. Preheat Oven And Preparing Baking Dish: Place oven rack on middle rack, preheat oven to 450 degrees F, and generously coat 8×8-inch baking dish in nonstick cooking spray.
2. Steam Frozen Vegetables: Microwave frozen cauliflower florets then frozen broccoli florets until tender, according to instructions on bags.
3. Cook Bacon: While vegetables cook, in a large skillet over medium heat, cook bacon until crispy. Transfer cooked bacon to a paper towel-lined plate, then crumble into pieces.
4. Mix Casserole Ingredients Together: In a small mixing bowl, stir together shredded cheeses. Then, in a separate mixing bowl, mix together sour cream, cream cheese, mayonnaise, and spices. Open bags of steamed vegetables and pour out any extra water. Then, into bowl of cream sauce, fold in veggies, half of the crumbled bacon, and ~1 cup of shredded cheese mixture.
5. Transfer Mixture To Baking Dish: Transfer cream sauce mixture to prepared baking dish and, using a rubber spatula, spread into an even layer. Sprinkle remaining shredded cheese mixture, then remaining bacon crumbles on top.
6. Bake Casserole: Cover dish with foil, transfer to oven, and bake for 12-15 minutes. Then, remove foil, move oven rack to top rack and turn on oven broiler. Broil casserole until cheese on top is bubbly and golden, about an additional 1-2 minutes, watching carefully to ensure it doesn’t burn.
7. Garnish And Serve: Remove dish from oven, allow casserole to cool slightly before garnishing with chopped green onions and serving.