Cracked eggs are put together again within these cups of smooth, cheesy custard.
Preheat oven to 325 degrees. Melt butter in a medium saucepan over medium heat. Whisk in flour, and cook for 1 minute. Slowly whisk in milk and 1 1/4 teaspoons salt until smooth. Cook, whisking occasionally, until mixture is thick enough to coat the back of a spoon. Remove from heat, and add cheese. Whisk until smooth.
Whisk together egg yolks and egg in a medium bowl. Bring cream to a gentle simmer in a small saucepan. Gradually whisk hot cream into eggs. Whisk cream mixture into cheese mixture.
Divide custard evenly (about 1/4 cup each) among 16 eggcups or small ramekins. Place cups in a large baking dish or roasting pan. Add enough boiling water to come halfway up the sides of cups. Bake until set, about 25 minutes. Remove from water bath, and let cool. Garnish with crisped prosciutto.