In glass bowl put in the first 2 ingredients. Microwave for 5 minutes. Take out and stir, then add the butter and microwave for 5 more minutes. Take out and mix in nuts if desired. Place in buttered 8 x 8 inch pan and place in refrigerator overnight (if needed sooner - put in freezer for awhile) cut into small squares.
Optional - add small marshmallows or white chocolate chunks when the nuts are added.
C/R