hee-hee shudda' guessed there's bees a number of mac&cheese heads (g)
here's some stuff that goes in my white sauce - just for ideas - not "everything in same batch" obviously....
the "stds"
AP flour + unsalted butter.
fgbp -
no salt - cheese has plenty
dry mustard - 2/3 to 1 T for a 3Tflour+3T butter batch
cayenne pepper - a threat to a liberal dose, depending on how 'hot' wanted
onion family:
shallots - nice waif of garlic . . .
spring onion aka green onion aka scallion - these taste different than bulb onion
yellow onion - some bite required
the onion stuff I always do in a very fine dice so it brings flavor but not "chunks" to the dish
other veggie stuff:
finely diced celery
celery seed
med fine dice of sweet pepper - red/green/yellow
diced banana peppers
'hot' peppers I reckon would work but no experience there
pimento
mushrooms - fresh portebello - de-stemed, diced, not pre-cooked
meat type stuff:
bacon - must be pre-fried crisp, drained & cooled
pepperoni - diced
(loose) sausage - pre-fried, drained & cooled
the liquids:
usually 1% milk
milk+light cream for company aka "extra rich&smooth"
heavy cream + water (in a pinch)
milk+white wine - add milk first, incorporate, then thin with wine else = breakage
the cheeses:
once upon a time I wandered into the 4-5-6 cheese counts. not recommend.
three seems to be magic max number.
I like to slice/dice/chop/shred/whatever the cheeses into thin section pieces so they melt quickly. this is really big time important for cheese that go stringy when melted - swiss is one - as larger chunks of such get to be a major headache in melting.
procedures:
stuff like onion, pepper and celery benefits from a high temp cooking down/softening.
this is problematic because adding these to the cooked roux, the moisture content has a immediate clumping up effect - so I do exactly that - but one cannot walk away - the clumped up roux needs one's undivided attention/stirring else = burnt stuff.
I like to add some liquid to the roux & whisk it in to get a stir-able sauce, then add the seasonings ala dry mustard, cayenne pepper, etc. then I add more liquid for volume before adding cheeses.
depending on cheese used, some - as the melt/incorporate - will result in a noticeably thicker sauce - I always have some milk/whatever at the ready for thinning down.
some high fat cheeses like to go "grainy" when melted. one can often "solve" that issue by increased heat and constant stirring to produce a smooth homogenous sauce BUT don't even blink much less walk away because over-doing the "jacked up the heat" will cause the sauce to break in a millisecond. if you go this route, up the heat, stir constantly, watch constantly, as soon as the grainy-ness disappears removed from the heat and continue to stir constantly until the pot / sauce has cooled slightly.
the consistency challenge:
if you bake the mac&cheese, the cooked pasta will absorb moisture from the sauce.
it is possible to create mac&glue; done that.
one has to experiment with the specific pasta, the pasta cooking times / draining times.
the other thing to note is - any leftover mac&cheese will markedly solidify/cool. I only "reheat" mine in a non-stick pan adding water to "re-loosen" the sauce.
apologies if I've violated anyone's "rules" - unlike a number of cooks in other Fori - I readily acknowledge that I do not know everything about everything - the only thing I know for sure is I don't know everything about everything - so it's a constant learning experience for me, at least.
love to heard about different approaches and mousetraps!