01 - 
                Line a 13×9 inch pan or 14×10 inch pan with parchment paper or spray with baking spray. I like to leave a bit of overhang of parchment paper on the short sides of the pan so I can easily lift the bars out.
              
              
              
                02 - 
                Stir together the cereals and peanut butter chips.
              
              
              
                03 - 
                Over low heat in a large saucepan, melt the butter. Add the entire package of marshmallows and use a spatula to stir well. Stir until marshmallows are completely melted. Add the peanut butter, stir until well combined and remove from heat.
              
              
              
                04 - 
                Add the peanut butter mixture to the cereal mixture, stirring quickly to get all the cereal nice and coated.
              
              
              
                05 - 
                Dump the mixture into the prepared pan and use your hands to press it into a flat, even layer.
              
              
              
                06 - 
                Add the chocolate and coconut oil to a microwave-safe bowl. Microwave for 1-2 minutes, stirring at each 30-second interval until chocolate is completely smooth and melted. Pour over the cereal treats and spread evenly across the top.
              
              
              
                07 - 
                Top with crumbled Reese's peanut butter cups, gently pressing the candy into the chocolate top. Sprinkle with flaky sea salt, if desired.
              
              
              
                08 - 
                Refrigerate for an hour or until completely set. Slice into bars.