Preheat the oven to 400 degrees.
Steam the fresh broccoli by microwaving it in a large bowl for 3 minutes. (If you like your broccoli more well done, try 5 minutes, but it continues to cook in the oven later on.)
Pour 1/4 cup of olive oil in a large skillet over medium-high heat. Add the frozen cauliflower rice and sauté until thawed, about 5-7 minutes.
Once the cauliflower rice has thawed, sprinkle 1/4 cup of flour, 1/4 teaspoon garlic powder, 3/4 teaspoon salt, and 1/2 teaspoon pepper into the skillet. Stir until the flour has absorbed all of the oil; it should look lumpy.
While stirring continuously, pour in the 2 cups of broth and 1/4 cup of milk. Keep stirring until the mixture reaches a simmer and thickens to resemble gravy, about 7-8 minutes.
Turn off the heat and add 2 cups of cheddar cheese and 1 cup of Parmesan. Stir until the cheese has melted, then add the steamed broccoli florets.
Mix everything together and pour it into an oven-safe casserole dish.
Optional: Mix together 1 teaspoon olive oil, 1/2 cup panko bread crumbs, and 1 Tablespoon parsley. Sprinkle this on top of the cheesy broccoli mixture.
Bake for 25-30 minutes and enjoy!