I'm not quite sure where the original recipe came from but I make it from time to time when we're craving a big breakfast. It cooks through the night and goes great with poached eggs. I used shredded potatoes but cubed hash browns can certainly be substituted.
Lightly butter or spray a 4 quart crockpot or slow cooker. I use crockpot liners - makes cleanup a breeze. Layer one 4th of the potatoes, followed by one third of the onion, one third of the cheese, and one third of the corned beef.
Sprinkle with celery seed, salt and pepper. Repeat two more times, ending with the remaining potato and another sprinkling of celery seed, salt and pepper.
Mix together the soup and milk. Pour over the potato mixture. Cook on low for 7 - 9 hours.