In a pot add 1 table spoon of salt and cover potatoes with water and cook till tender. When done remove the potatoes and give them a rough mash (add a little butter and salt and pepper to taste) and set aside. Save water to steam the Spinach.
In a large sauté pan add 1 ounce of olive oil and add 1 1/2 cups of onions, Hot Sausage (take out of casing and crumble), cook for 5 minutes then add the mushrooms and cook till tender. Add more olive oil if needed. Set aside the pan will use it later
In a large pot (with potato water) steam all the Spinach and drain. When cool squeeze the spinach to get rid of most of the water
Now take the cool spinach and chop into pieces and add to the sauté pan with sausage and mushrooms and cook for 6 more minutes. Next add the potatoes to the mixture and mix well blending them together, until they are blended well. Now add 4 ounce stick of butter and keep turning until are fully mixed.
Serve with fresh Italian bread.