Best Broccoli Rice Casserole

Ingredients

• 2 cups cooked white rice
• 6 cups broccoli
• 1 onion
• 1/2 cream cheese
• 3 tablespoons all-purpose flour
• 1/2 cup sour cream
• 1 cup heavy cream
• 2 cups shredded cheddar cheese
• 1/4 teaspoon pepper
• 1/2 teaspoon dry mustard powder
• 1/2 teaspoon salt
• 1/2 teaspoon paprika
• 4 cloves garlic
• 1 cup milk
• 3 tablespoons unsalted butter