Add hamburger, water, and minced onions to the slow cooker and cook on low 2 hours. Occasionally breaking up the hamburger as it cooks. (In this recipe, the hamburger was put into the slow cooker frozen. If using fresh hamburger, the cooking time is only 1 hour on low).
Add the cream of mushroom soup and water or milk and cook another 30 minutes on low.
Add noodles with the additional water and cook another 30 minutes on low. This time mushrooms were added in the last 30 minutes too. You don’t have to, but you could certainly add any other vegetable to this in the last hour.
Garnish with fresh parsley if you have any on hand.