Preheat oven to 350 degrees F. Grease a 13x9 baking dish.
Brown the sausage, breaking it up into small pieces. Transfer the cooked sausage to a clean bowl. Wipe out most of the grease.
Add the butter to the same pan and melt over medium heat. Whisk in the cream of mushroom soup, milk and Worcestershire sauce until smooth and heated through. Remove from heat and set aside.
In a large bowl or glass measuring cup, whisk together the eggs, sour cream, parsley, salt and black pepper until very smooth.
Open the can of biscuits. Cut each biscuit into four pieces. Place the biscuits into the bottom of the greased casserole dish in an even layer.
Crumbled the cooked sausage evenly over top of the biscuits.
Evenly layer the shredded cheese on top of the sausage.
Gently pour the egg mixture over top of the casserole.
Then top everything evenly with the prepared gravy.
Bake the casserole uncovered for about 35 - 40 minutes, or until the biscuits have puffed up and the casserole is starting to brown.
The casserole can be made a day ahead. After topping it with the gravy, cover the dish with plastic wrap and refrigerate. Bake the next morning at 350 degrees for 45 - 50 minutes.