1. Grease a 9 X 13 cake pan lightly.
2. Use a large microwaveable bowl.
3. Heat butter and marshmallows in microwave on High for 3 minutes, Stir halfway through.
4. Add peanut butter and vanilla to marshmallow mixture and stir.
5. Add Rice Krispies and mix until they are well coated.
6. Pour into prepared pan and press down lightly (greased hands work well).
7. Enjoy.