Preheat your oven to 350°F (175°C). Grease a large baking dish with a bit of butter or non-stick spray.

Steam the broccoli until it's just tender, about 3-5 minutes. Alternatively, you can blanch it in boiling water for 2 minutes then rinse under cold water to stop the cooking process. Set aside.

In a large skillet, melt the butter over medium heat. Add the diced onion and cook until it becomes translucent.

Stir in the roasted garlic base and Dijon mustard. Sprinkle the flour over the onion mixture and stir to combine, cooking for about 1-2 minutes to remove the raw flour taste.

Gradually whisk in the half-and-half (or heavy cream), ensuring there are no lumps. Bring the mixture to a gentle simmer, and let it thicken slightly.

Stir in the sour cream, Parmesan cheese, and Monterey Jack cheese until the mixture is smooth and the cheese has melted. Season with celery salt, smoked paprika, and all-purpose seasoning to taste.

In the prepared baking dish, spread the cooked rice as the first layer. Top with the steamed broccoli.

Pour the creamy cheese sauce over the broccoli, ensuring it covers all the pieces evenly.

Sprinkle the shredded Colby Jack cheese over the top.

In a small bowl, mix the crushed garlic butter Ritz crackers with a bit of melted butter, if desired, for extra richness. Sprinkle this mixture over the cheese layer.

Place the casserole in the preheated oven and bake for 45 minutes, or until the top is golden brown and bubbly.

Remove the casserole from the oven and let it cool slightly before serving. Garnish with diced parsley for a fresh, colorful touch.