For the bread, preheat the oven to 300°F and line a baking sheet with parchment.
Beat the egg whites with the cream of tartar and salt until soft peaks
Whisk the cream cheese and egg yolk until smooth and pale
Fold in the egg whites a little at a time until smooth and well
Spoon the batter onto the baking sheet into two even
Bake for 25 minutes until firm and lightly
Spread the butter on one side of each bread circle then place one in a preheated skillet over medium
Sprinkle with cheese and add the sliced ham then top with the other bread circle, butter-side-up.
Cook the sandwich for a minute or two then carefully flip it
Let it cook until the cheese is melted then serve