Lightly steam spinach, separate and squeeze dry. Let cool to room temperature. Preheat oven to 300 degrees.
Beat egg whites until thick and foamy, but not as stiff as meringue. Beat egg yolks in food processor; add in cream, nutmeg, salt, and cheese and process until smooth. Process spinach into egg mixture. Using the food processor for this really purees the spinach and makes the soufflé lighter. Fold the whipped egg whites into the spinach-egg mixture until well combined. Pour mixture into a greased round 1 1/2-qt casserole; top with crumbs.
Bake for 45 minutes or until knife inserted in center comes out clean. Serve immediately.