Heat oven to 375 degrees. Bring a large pot of
lightly salted water to a boil. Add macaroni
and cook 8 minutes or as per package
directions. Drain and return to pot.
Meanwhile, melt butter in a saucepan
over medium heat. Add flour and cook
1 minute. Whisk in milk in a thin stream.
Whisk in mustard, onion powder, salt,
pepper, nutmeg and cayenne. Bring to a
simmer; cook 3 minutes, whisking
Remove from heat and whisk in
American cheese and 1 cup of the cheddar
cheese. Whisk a little of the cheese sauce
into the egg to temper. Whisk egg mixture
back into cheese sauce.
Stir sauce into macaroni. Coat
indents of 16 standard muffin cups with
nonstick cooking spray. Divide
macaroni among prepared cups. Top
each with 1 tbsp of the remaining
cheddar cheese. Bake at 375° for 18
minutes until lightly browned. Cool
slightly before running a thin spatula
around edge and spooning out of pans.