Mmmm...these were so yummy. I'm not a big peanut butter fan, so I substituted Hershey's Cinnamon Chips and the smell was HEAVENLY. I love how the crispy top layer tasted with the mashmallow. I read reviews in advance and ended up patting down the melted marshmallows with a large spoon dipped in butter. I had no problems with that step. Like other reviewers, I too had a problem with the bottom layer. I used a smaller pan and baked it longer, but it tasted like undercooked dough. Also I found that the whole bar lost its shape easily if the room temperature was too warm, so I kept it refrigerated. I would make this again with a much wider pan. Overall it was delicious.