Combine soup, stock, brown sugar, oregano and lamb shanks in slow cooker and turn on.
You can place slow cooker on low and let cook all day or place on high and cook for 4 to 6 hours.
Peal potatoes cut in to chunks. Place in to large saucepan with cold water. Place saucepan on stove top on medium to high heat and boil till soft.
When cooked drain water and mash while adding butter and milk to get a nice thick consistency.
Serve lamb shanks on a bed of mashed potateo.