Found this recipe in a supermarket magazine. Being a bit of a peanut butter addict I had to make them and being a chocolate addict I had to melt some chocolate and pour it over the top!
First, grease a tin for the crispies (an 18cm square tin was used in the original recipe).
Melt butter over a low heat.
Still over a low heat, add the marshmallows to the butter and stir until melted.
Remove from the heat and add the peanut butter. Stir until smooth and melty.
Add the Rice Krispies and stir until evenly combined.
Transfer the mix to the greased tin and level the top. If you are not adding the chocolate, it would be easier to cut them into squares now before they set. Then put them in the fridge to set.
If you like, melt a bar of chocolate and pour it over the top. I just used a bowl over a pan of boiling water to melt the chocolate then just poured it and spread it out over the crispies. Put them in the fridge to set for about half an hour, then cut them up into squares before returning them to the fridge to finish setting.