In a medium bowl, mix together egg, spinach, seasoning salt, onion powder and pepper Add mashed potatoes and mix until well combined. Stir in cheese, bread crumbs and chives. Mix until combined and bread crumbs have been absorbed.
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.
Stir together sour cream and dill and season to taste with salt and pepper. Keep chilled until ready to serve with cakes.