Preheat your oven to 350°F (175°C).Cook the rice according to package instructions using the water.In a large skillet, melt the butter over medium heat. Add the onion and garlic, sauté until translucent.Add the chopped broccoli to the skillet, cooking for 5-7 minutes until slightly tender.In a large mixing bowl, combine the cooked rice, sautéed vegetables, cream of mushroom soup, sour cream, and 1 1/2 cups of shredded cheddar cheese. Mix well.Season the mixture with salt and pepper to taste.Transfer the mixture to a greased 9x13-inch baking dish.Sprinkle the remaining cheddar cheese on top. If using breadcrumbs, sprinkle them over the cheese for a crispy topping.Bake in the preheated oven for 30-35 minutes, or until the casserole is bubbly and the top is golden brown.Let it rest for 5 minutes before serving.
Notes
For a deeper flavor, consider adding a teaspoon of Dijon mustard to the mixture.