Preheat the oven to 350°F (175°C). Grease a 9x13-inch baking dish.
In a large pot, bring water to a boil. Add the cauliflower and broccoli florets and cook for about 5 minutes until tender. Drain and set aside.
In a large mixing bowl, combine the softened cream cheese, sour cream, garlic powder, onion powder, salt, and pepper. Mix until smooth.
Stir in the cooked cauliflower and broccoli, crumbled bacon, and half of the shredded cheddar cheese. Mix until well combined.
Transfer the mixture to the prepared baking dish and spread it evenly. Top with the remaining cheddar cheese and panko breadcrumbs if using.
Bake in the preheated oven for 25-30 minutes, or until the cheese is bubbly and the top is golden brown.
Remove from the oven and let it cool for a few minutes before serving. Garnish with chopped green onions.