My first thought was that broccoli would have been a better choice. But even so.... I'm a bit skeptical of any high fiber addition to mac n' cheese. It seems like it'd detract from the texture. I could possibly see mushrooms working as the softer feel might work well with everything else. And a cheese and mushroom combo can work.  Then again, noodles and stir fried vegetables go great together. So who knows, cauliflower might go ok with it. I know this is off topic, but anyone tried this before? I'm kind of curious now.