Melt your marshmallows and butter in a small pan over medium low heat. It will take several minutes and lots of stirring before you see the marshmallows start to melt.
Keep stirring, and make sure you scrape the bottom of the pan so it doesn't stick.
Once it's all melted together and smooth, gently fold in your granola.
Spray an 8 x 8 inch pan with nonstick cooking spray to prevent sticking, and press your granola into the pan. Be sure to spread it out evenly.
Let them sit for an hour or two before eating.
Notes
These will keep at room temperature in an airtight container for a few days.