Preheat oven at 400°F. Generously grease a mini muffin pan.
In a large bowl, combine mashed potatoes, eggs, ham, Cheddar, Gruyere cheese, flour and chives. Season with salt and pepper. Mix and combine well.
Put a spoonful of the potato mixture in each cup. Sprinkle tops with Parmesan cheese.
Bake 25-35 minutes until golden brown, and cups are set.
Remove from the oven, let stand for 5 minutes. Remove the cups with a knife or spatula.
Serve with sour cream and chives.