• Cook the long-grain white rice according to package instructions, stopping a few minutes early to keep the rice al dente. Drain any excess water and set the rice aside.
• Bring a medium pot of water to a boil. Add the broccoli florets and a pinch of salt, and cook for 3-4 minutes until tender but still slightly crisp. Drain the broccoli and rinse with cold water to halt the cooking process. Set aside.
• Preheat the oven to 350°F. Lightly grease a 9x13-inch baking dish with butter or non-stick cooking spray. Set aside.

Make the Sauce

• In a large skillet, melt the butter over medium heat. Add the diced onion and sauté for 3-4 minutes until translucent. Add the minced garlic and cook for an additional 1-2 minutes, stirring constantly.
• Sprinkle the flour over the onion and garlic mixture, stirring continuously to create a roux. Cook for about 2 minutes until the flour is golden and fragrant.
• Gradually pour in the milk while whisking to prevent lumps. Add the chicken broth and continue to whisk until smooth.
• Season with salt, pepper, thyme, and paprika. Bring the sauce to a gentle simmer and cook for 5-7 minutes, stirring frequently, until it thickens to a creamy consistency.
• Remove the skillet from heat and stir in the softened cream cheese until fully melted.
• Fold in the shredded mozzarella and grated Parmesan cheese, stirring until the cheeses are melted and the sauce is smooth.

Assemble the Casserole

• Pour the prepared sauce into the greased baking dish. Add the cooked broccoli and previously prepared rice into the sauce.
• Gently stir the mixture in the baking dish until the rice, broccoli, and sauce are evenly combined.
• Sprinkle the Mexican blend cheese over the top of the casserole.

Bake the Casserole

• Place the casserole in the preheated oven and bake for 25-30 minutes, or until the cheese on top is melted and bubbly, with a golden-brown crust forming around the edges.
• Remove the broccoli rice casserole from the oven and allow it to cool for 5-8 minutes before serving.