1. Preheat oven to 350°. Lightly grease a 12-cup muffin pan or 12 ramekins. Place prosciutto slices into bottoms and up sides of cups, overlapping in a crisscross pattern.
2. Combine eggs, salt, and pepper. Divide spinach and cheese among muffin cups. Pour egg mixture evenly into muffin cups.
3. Bake pies 14 to 16 minutes or until just set. Let stand about 5 minutes. Loosen pies by running a knife around the edges of each cup, and then lift out of pan with a small spatula. Serve immediately.