Preheat the oven to 350F.
Spray an 8 x 8 casserole dish with cooking spray or grease with butter.
Combine the topping ingredients in a small bowl and set aside.
In a large skillet over medium heat, cook the onion with the butter until the onion is translucent (about 8 minutes)
Add in the minced garlic and cook for 1 minute more.
Add in heavy cream and cream cheese.
Stir to melt the cream cheese.
When the cream cheese is melted, remove from the heat and stir in the shredded cheese.
Add in the steamed broccoli and cauliflower rice to a large mixing bowl.
Pour the cheese sauce on top and mix well.
Pour into the casserole dish.
Sprinkle the parmesan topping evenly over the top.
Bake in the pre-heated oven for 30 minutes.