Your first recipe has only eggs to hold the cheese emulsion together, and it doesn't have you incorporating them into a stable sauce so it's no wonder it split (it probably never fully came together). The only cooking here is to barely set the egg (which the hot pasta should be nearly capable of doing on its own) and to heat to serving temp. I am guessing the pasta looked delicious and great before the 3 hour cook, right? I would reduce the cook times from both to ~5 minutes. They have you incorporate ingredients that are either fully cooked, or will cook almost instantly after being introduced to hot pasta, then for some reason simmer for 3 hours after? That 3 hours of cooking isn't doing anything except for making your pasta mushy and splitting your sauce. My $.02 is that these recipes don't make any sense. Note: for logistical reasons, I'd RATHER make it in a crockpot instead of bake it in the oven, since I cook and clean the whole holiday alone. Please help! I only have 364 days to get it right! So what am I doing wrong that 90% of other people are doing 'right'? I'm no chef, but I'm pretty good in the kitchen. I seems less than 10% of the people said theirs also curdled. Result: curdled/broken at 3 hours, when I served it. Reflection: I thought I may have cooked it too long so I reduced the timing this year. Result: looked good 1/2 way in, but when I went to serve, it was WAY broken/curdled. For 2 years in a row now (the only times I make macaroni and cheese), my end-result is a curdled/broken mess. For Christmas Eve dinner, I make a beef tenderloin, cranberry compote, Brussels sprouts, and macaroni and cheese.

Trisha yearwood crockpot mac and cheese