So, garlic and/or onion in mac-n-cheese, I go back and forth on this, I really like to use finely choopped onions and garlic in my, for my own consumption. However, I have had comments that there is a funny taste from some folks, so I err on not adding it, or adding very little, when serving to a large number of people. Plus, I know that garlic and onion can be a 'non-starter' for some folks, and I like to leave a safe-option dish when I am serving other folks.
For strictly home and family, I usually add 1/4 cup each of finely chopped celery and onion, a couple to three cloves of salt crushed garlic and some parsley and tarragon minced up to the roux cooking stage.
I'm feeling bearish, and I'm packing a Wusthof Grand Brisket slicer from MABA
"perhaps...but then again...maybe not..."