• Preheat oven to 350 degrees Fahrenheit. Ready a 9x13-inch casserole dish by coating it with nonstick cooking spray.
• In a large skillet on medium-low heat, melt the butter. Then add onions and cook until tender, about 5 minutes. Stir in flour and seasonings and cook for an additional 2 minutes.
• Gradually add in the milk, and whisk mixture until thick and bubbly.
• Take the skillet off the heat, then blend in the cream cheese and half the cheddar cheese until they're completely melted and smooth.
• In a large bowl, combine the rice, broccoli, and cheese sauce from skillet. Then transfer this mixture to the prepared casserole dish.
• Sprinkle the remaining shredded cheddar cheese over the top.
• Bake the casserole for 45 to 50 minutes or until the edges are bubbling.

To Make Ahead

• Prepare the casserole as directed.
• Cover tightly and store in the refrigerator for up to 3 days or freeze for up to 6 months.
• Allow to thaw in the refrigerator before baking.
• Uncover and bake according to directions.