MIX eggs, spinach and onion until well blended.
HEAT oil in large nonstick skillet on medium-high heat. For each pancake, pour 1/4 cup of the egg mixture into skillet; sprinkle with about 1 Tbsp. of the cheese. Cook 2 min. or until golden brown. Turn pancakes; cook until other side is golden brown.
SERVE topped with sour cream.