I use a mini-blender.
rather classic . . . olive oil+yolk+white wine vinegar+dijon+garlic+anchovy filets x 3-4 or more....I like 'em
but I don't add the parm to the dressing - I grate it off a block at home. no green can stuff.
sprinkle on romain prior to dressing.
curiously ... of late I have been using extra virgin olive oil (Kirkland). it quite noticeably makes for thicker/creamier than my usual olive oil.
don't know why or the mechanics of it - but it makes a serious difference.
edit to add: the mustard acts as an emulsification "aid" - I don't recommend going light on the Dijon.