i have a recipe for something called toffee mallow crunch, made using the microwave, which contains those ingredients:
4 oz. soft toffees
4 oz butter
4 oz marshmallows
5 oz rice crispies
warm toffees and butter for 1-2 minutes in micro. stir, and add marshmallows. warm for a further minute then stir again (it should all have melted and mix together easily, if not micro it for a further 30 seconds or so). add half the rice crispies, stir to coat, then add the rest and stir again. press intoa greased dish and leave to cool.
took me right back to making these with the kids when they were young, used to make them nearly every week :)