Preheat oven to 340 degrees F or 170 degrees C.
Brush soufflé dishes with softened butter and place in the refrigerator.
1. Melt butter in a heavy based saucepan, stir in flour and cook for approximately 3 minutes or until the roux resembles wet sand, remove and cool.
2. Bring milk to a boil. Gradually whisk hot milk into the roux. Bring to boil over medium heat, whisking continually.
3. Season with salt, pepper and nutmeg.
4. Lower heat, simmer the thick soufflé base for about 2 minutes, whisking constantly.
5. Add grated cheese and egg yolks. Mix well.
6. Remove from the heat, immediately whisk in chopped ham.
7. Whisk egg whites with a pinch of salt to form stiff peaks.
8. With a spatula, stir one third of the whipped egg whites into soufflé base.
9. Fold in remaining whipped egg whites, taking care to gently lift and fold.
10. Fill prepared soufflé dishes to the top, level surface with a metal spatula.
11. Use your thumb to run around the dish's edge. This will help the soufflé to rise correctly.
12. Decorate soufflés with cheese and ham diamonds. Bake in preheated oven for approximately 20 minutes. Serve immediately.
The key to a successful soufflé is to beat egg whites correctly and to have a good folding technique.
Perfectly beaten egg whites are smooth and shiny, not dry and a hold a stiff peak when the whisk is raised from the bowl; a separated or grainy appearance indicates that the whites have been overbeaten.
The purpose of folding is to incorporate the beaten whites into the soufflé base while losing as little volume as possible. Always whisk a little of the beaten whites into the soufflé base before folding in order to loosen the mixture and to make it nearly the same consistency as the whites. Then add the remaining egg whites and fold them in: Cut straight down to the bottom of the bowl with a spatula, lift up the contents of the bowl and fold over while giving the bowl a quarter turn (with your other hand). Continue this motion until the whites and soufflé mixture are well blended.