Add butter to crock pot/ slow cooker.

Add marshmallows over butter.

Pour crisps, one cup at a time, alternating over the marshmallows.

Make sure crisps cover marshmallows.

Cover and cook for an hour on high.

Check to be sure marshmallows have melted.

Stir to combine.

Remove from crock pot/ slow cooker and place in pyrex dish to cool.

Once, cooled cut into squares and serve.

Note: Used One degree brown rice crisps.