I adapted this from another recipe. I made it for a family gathering and now it is all I am asked to bring... not that I can't cook, it's just THAT good! I for one, especially like the crispy cheese that sticks to the sides of the crockpot, yum!
Boil maccaroni per package directions. Use shortest cook time suggested as pasta will cook in the crockpot.
While pasta is cooking, in bowl large enough to hold all ingredients; using a wire wisk, beat 3 eggs together with milk, salt, pepper, dry mustard and sour cream.
Stir in soup and 2-1/2 C. cheese.
Melt butter in small sauce pan on stovetop. When pasta is finished cooking, drain well and carefully stir pasta and melted butter into bowl with all other ingredients. Stir quickly so as not not cook the eggs.
For easy clean-up, spray a 4qt. crock pot with non-stick spray. Carefully pour mixture into crockpot, cover and cook on low 3 hours. At the 2-1/2 hour mark spread remaining 1/2 C. shredded cheese over top of mixture and return lid to cook the last half hour.