Bring water and rice to a boil in a saucepan. Reduce heat to medium-low, cover, and simmer until rice is tender and water has been absorbed, 20 to 25 minutes. Set aside.

Meanwhile, place a steamer insert into a saucepan and fill with water to just below the bottom of the steamer. Bring water to a boil. Add broccoli, cover, and steam until slightly tender, 3 to 4 minutes.

Preheat the oven to 350 degrees F (180 degrees C) and grease a 9 x 13 baking dish.

Melt butter in a large skillet over medium heat. Add diced onion and cook until soft and translucent, 3 to 4 minutes. Add the garlic and cook for another 30 seconds.

Stir in cream of mushroom soup, sour cream, and milk. Mix until smooth.

Add 2 cups of shredded Cheddar cheese, salt, pepper, and paprika. Stir in the cheese until it’s melted and the mixture is mostly smooth.

In a large mixing bowl, combine the cooked rice, steamed broccoli, and cheese mixture. Stir until well combined.

Transfer the mixture to the prepared baking dish and spread evenly.

Mix crushed garlic Parmesan pretzels, melted butter, and grated Parmesan cheese in a bowl until combined. Sprinkle topping evenly over the casserole.

Bake uncovered for 25 minutes until pretzel topping is golden brown. Add remaining cup of cheese and bake until cheese is melted, 3 to 5 minutes.