In a pan, melt peanut butter. Stir in rice cereal when the peanut butter has melted. Stir in peanuts if desired. Transfer mixture into an 8x8 inch casserole dish.
In the top of a double boiler (or microwave - be sure to stir constantly), melt the chocolate chips. Pour the melted chocolate over the top of the candy in the dish and swirl with a fork.
Chill and cut into squares to serve.