Spread your slices of bread with butter.
Mash avocado using a fork until it's mushy and smooth.
Place one piece of bread, butter side down, into your sandwich press.
Spread avocado evenly on the slice of bread in the sandwich press.
Cover avocado evenly with cheese slices.
Add the other piece of bread on top, butter side up.
Close the sandwich press and cook until golden brown.
Let cool for a few minutes before serving.