In a medium saucepan, melt butter over medium-low heat. Whisk in flour to form a roux. Continue to whisk until roux is a light brown (blond roux.)
Slowly pour milk into the roux, whisking until smooth. Batter will be thick. Whisk in salt, nutmeg and black pepper. Remove from heat.
In a separate bowl, whisk egg yolks until pale and fluffy. Fold into roux along with shredded cheddar cheese and ham. Set aside.
Whisk egg whites and cream of tarter until soft, fluffy peaks form. This process is incorporating air into the mixture, which is what increased the volume significantly.
Prep 6 4-ounce ramekins with cooking spray and place onto a rimmed baking sheet. Spoon mixture evenly into each ramekin. Fill approximately 3/4 of the way.
Bake for 30 minutes. Remove and top each with a pinch of cheddar cheese, crumbled bacon and chives.
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