Step 1

Preheat oven to 350 degrees F. Lightly spray a 9x13 pan with nonstick cooking spray; set aside.

Step 2

Melt butter in a very large skillet or Dutch over medium heat (something that can fit all ingredients). Whisk in flour then cook, while stirring for 2 minutes. Reduce heat to low then gradually whisk in milk and 1 ½ cups chicken broth. Whisk cornstarch with remaining chicken broth and add to skillet followed by Dijon, Worcestershire sauce, chicken bouillon and all spices/seasonings.

Step 3

Bring sauce to a simmer, whisking constantly, until thickened. Remove from heat and whisk in cheddar until melted followed by Gruyere cheese until melted. Whisk in sour cream until blended. Stir in defrosted hash browns until completely combined.

Step 4

Transfer hash browns to prepared baking pan and spread into an even layer. Evenly top with 1 cup shredded cheddar. Combine Ritz with melted butter and stir with a spatula until evenly coated. Sprinkle evenly over cheese.

Step 5

Cover casserole with foil and bake at 350 degrees for 40 minutes, uncover and bake an additional 15 minutes or until hot and bubbly and cheese is melted. Turn oven to broil (without moving pan) and broil until topping is golden, 1-2 minutes, watching closely it doesn't burn.