Cut the slices of cheddar cheese; not too thick, but not skimpy, either; cut one slice in half.
Take the two slices of bread and generously butter each of them on one side.
Heat up a cast iron skillet over medium heat.
Get yourself the cover from a Revereware saucepan, or another cover of about the same size.
Place one of the slices of bread, butter side down, in the hot skillet.
Spread 2 and a half slices of cheese on the bread, then cover it butter-side-up with the other slice of bread; eat the extra, unused half of the cheese slice.
Push the bread down a little with the metal spatula, then cover the whole thing up with the saucepan lid (the idea is to heat the air up underneath the lid and melt the cheese faster as you're also browning the bread).
Uncover every minute and check the cooking bread color- you want it golden, not burnt (no matter what Mom says - she likes 'em black for some reason).
When it's to the color you like, carefully flip the sandwich over, press down on it with the spatula to squish the bread and cheese together, and re-cover with the saucepan to continue melting the cheese.
After about 3-5 minutes of slow cooking, you'll have a wonderfully golden, melty, gooey grilled cheese sandwich!