Crockpot Hash Brown Casserole

Name: Crockpot Hash Brown Casserole
Ingredients: Cooking spray; 6 tablespoons unsalted butter; 1 cup finely diced yellow onion; 1/2 cup diced mushrooms (I use baby bella); 3 cloves finely minced garlic; 1 teaspoon garlic powder; 1 teaspoon onion powder; 2 teaspoons chicken bouillon powder; 2 teaspoons dried parsley; 1/4 teaspoon dried thyme; Salt and pepper; 1/3 cup all-purpose flour; 1-1/2 cups whole milk; 1-1/2 cups chicken broth; 1-1/2 teaspoons Dijon-style mustard; 1 cup sour cream; 2 (20-ounce) packages refrigerated shredded hash browns (); 3 cups freshly shredded sharp Cheddar cheese; 7 slices cooked and chopped bacon (optional topping); Fresh chives (optional topping)