My grandmother brought this 4-ingredient dish to our cookout and it disappeared in seconds.

Spray the inside of a 4- to 6-quart slow cooker lightly with nonstick cooking spray or rub with a bit of butter to help keep the noodles from sticking.
Pour the uncooked wide egg noodles into the bottom of the slow cooker and spread them into an even layer so they cook more evenly.
Scatter the pieces of salted butter evenly over the dry noodles so they can melt down into all the nooks and crannies.

Sprinkle about 3 cups of the shredded Swiss cheese (reserving the remaining 1 cup for later) evenly over the noodles and butter.
Slowly pour the whole milk over everything in the slow cooker, making sure most of the noodles are moistened. Gently press down with the back of a spoon to help submerge the noodles as much as possible without stirring too much.
Cover the slow cooker with the lid and cook on LOW for 2 to 2 1/2 hours, until the noodles are tender but not mushy and the cheese and milk have formed a creamy sauce around them. About halfway through, gently stir from the bottom with a wooden spoon, then replace the lid quickly to keep the heat in.

Once the noodles are tender and the mixture looks creamy and saucy, sprinkle the remaining 1 cup of shredded Swiss cheese over the top. Cover again and cook on LOW for another 10 to 15 minutes, just until the cheese on top is fully melted and stretchy.
Give the noodles a gentle stir to pull that top layer of melted Swiss down into the pot. The sauce should look glossy and rich, and when you lift a spoonful, the cheese should stretch a bit between the noodles.
Taste and adjust the seasoning if you like (the salted butter and Swiss usually give enough saltiness). Switch the slow cooker to WARM for serving, and stir occasionally to keep the noodles from sticking to the sides. Serve hot straight from the slow cooker.
Variations & Tips