In a medium bowl, mix together egg, spinach, dill,green onion and seasonings. Add mashed potatoes and bread crumbs, mix until well combined. Fold in cheese.
Heat oil in a non stick frying pan over medium-high heat. While pan is heating, form 1/3 cup potato mixture into approximate 3" patties about 1/2" thick and place into pan as you form them. Cook 4-5 minutes per side until heated through and golden brown. Serve with sour cream and additional fresh dill and sliced green onions.