This recipe comes from Kenda, Peg’s best friend (probably mine, too), and it gets rave reviews everywhere. We normally make a double batch. Peg has some notes. I have some footnotes.
8oz pkg elbow macaroni, cooked until still firm
12oz. can evaporated milk 
1 cup whole milk
1/4 cup butter, melted
2 large eggs, slightly beaten
4 cups grated sharp cheddar cheese, divided 3c/1c
1/4 to 1/2 tsp. salt
1/8 tsp. white pepper 
1/4 cup Parmesan cheese grated
In the slow cooker, combine lightly cooked macaroni, evaporated milk, whole milk, melted butter, eggs, 3 cups cheddar cheese, salt and pepper.
Top with remaining cheddar cheese and parmesan cheese. 
Cover. Cook on low 3 hours. Watch the pot – one pot’s “low” can burn
the outside and make it like rubber.
I doubled this recipe when I made it to take to a party.
It really doesn’t need the butter. It makes a very rich mac & cheese dish without the butter in it!!
I once put 1/2tsp of ground mustard into a double batch, but there was no discernible difference. I was hoping for just a little more “zing”, thinking it would play off of the ham, but didn’t go strong enough.
 Original recipe called for 13oz. Evaporated milk comes in 12 oz cans. Don’t kill yourself over detail if it’s not baking.
 Really, does anybody still have white pepper? Black pepper works just fine.
 Peg normally mixes the Parmesan in with the main ingredients.
 Ask John how he knows.
It reheats well in the microwave, too.!