1⁄3 cup Black Forest ham, thinly sliced and cut into 1⁄2" squares
1⁄3 cup finely shredded Gruyère
Preheat the oven to 375°. Generously butter a 1 1⁄2-quart soufflé dish. Break each egg over a large bowl, and pass the yolk back and forth between the shell halves until all the egg white has dropped into the bowl and only the yolk remains in the shell. Place yolks in a separate bowl.
Beat yolks gently with a whisk. Whisk in flour, salt, pepper, and nutmeg. Add sour cream and ham, and stir to combine.
In a separate bowl, beat egg whites with an electric mixer on high speed until they form stiff peaks, about 2 minutes. (Stop the mixer and lift the beaters up. You should see a distinct peak with an ever-so-slightly droopy top.)
Add one quarter of the egg whites to the yolk mixture, and fold in gently. Add the remaining egg whites and cheese, and fold in gently. Do not mix more than absolutely necessary.
Pour mixture into the buttered soufflé dish. (At this point, you can cover the soufflé dish and refrigerate for a few hours or overnight.) Before baking, let it sit out for an hour and a half. It should come up to about an inch below the rim. Bake for 35 minutes.