Measure out your rice crispies and put them in a large bowl. Butter a 9 by 13 baking dish and set aside.
In a medium saucepan, add your butter, marshmallows and sweetened condensed milk. Cook on low heat to medium heat until it comes to a boil. Continue to cook for 2-3 minutes.
Pour this marshmallow mixture over the rice krispies and start to stir. Once they are about half combined, add the peanut butter chips and a pinch of sea salt. This is my secret ingredient. Continue to stir until all is combined. The chips will melt from the heat of the sauce, but they may not melt all the way which is nice.
If you find that the combined mixture is too wet, add more rice crispies.
Pour this into your 9 by 13 pan and spread out with a spatula. Once its spread out in an even layer, use buttered hands or buttered parchment paper and press down into the treats to compress them. You dont have to compress them a lot, but this will just help it hold its shape better and I find the texture of the treats to be better when its done this way. Technically some of the rice crispies get smashed and create a better texture.
Once they have cooled, you can cut them into pieces and serve!
Store in a airtight container for 3-4 days. Mine never last that long anyways!