Heat oven to 200F° and place an empty 9x13 or large casserole dish inside. This is your serving dish and you want it to be hot.
In a large pot bring water to a boil and add the salt. You will be cooking your spaghetti in this pot.
Meanwhile in a small bowl cream butter by beating it for about a minute with a spoon or fork. Set bowl aside.
In a medium size bowl stir together 2 whole eggs and then 2 egg yolk. Stir in ½ cup Parmesan. Set bowl aside.
Drop spaghetti in boiling water and cook for about 10 minutes or until tender.
Discard half of the bacon fat.
Stir in cream and let simmer until the spaghetti noodles are done.
Pull out your heated casserole dish from the oven and add the cooked spaghetti noodles.
Pour in the egg Parmesan cheese mixture. It will be thick because of the cheese. Be sure to toss and stir it in completely and evenly.