In a medium mixing bowl, mix together the eggs, evaporated milk, salt, red pepper flakes, black pepper and one cup of the shredded cheddar and mozzarella cheeses. Set aside the remaining cheese for later.
Scrub the potatoes and slice thinly.
Place half of the sliced potatoes in the bottom of a 3.5 quart casserole slow cooker OR a 6 quart or larger slow cooker.
Spread half of the browned ground sausage on top of the potatoes.
Sprinkle half of the yellow onion and then 1/2 of the remaining cheddar and mozzarella Cheese.
Repeat the layers with a the remaining potatoes, sausage, onion and cheeses.
Carefully pour the egg mixture over your entire potato and sausage mixture. You'll want to get all of it covered.
Sprinkle the green onions on top.
Cover and cook on LOW for 5 to 6 hours or on HIGH for 3 hours or until the eggs are set. A meat thermometer registering at 160° F means it's done.
Sprinkle the top of the cooked casserole with freshly grated Parmesan cheese and paprika before serving if desired and enjoy!
Notes
To make clean up easier you may wish to either line your slow cooker with a slow cooker liner or spray with non-stick cooking spray. Weight Watchers points calculated using fat-free evaporated milk, cheddar and mozzarella cheese.