To prepare the chaffle, whip the egg white until frothy. Add the sour cream and almond flour and blend well. Mix in the cheese.
Preheat the mini waffle maker as per manufacturer's directions. When hot, add half the batter and cook for 7-10 minutes or until the chaffle is golden brown and releases easily. Repeat with the remaining batter.
Meanwhile, warm the beef broth in a small skillet or pot. Add the sliced beef to heat through - but don't over cook it!
To assemble, place the drained beef on the chaffle, top with cheese (optional) and serve with the remaining broth on the side.